Immunoconjugates comprising anti-her2 antibodies and pyrrolobenzodiazepines

ABSTRACT

The invention provides immunoconjugates comprising anti-HER2 antibodies and methods of using the same.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of International Application No. PCT/US2015/050382, filed Sep. 16, 2015, which claims the benefit of priority of U.S. Provisional Application No. 62/051,562, filed Sep. 17, 2014, each of which is incorporated by reference herein in its entirety for any purpose.

SEQUENCE LISTING

The present application is filed with a Sequence Listing in electronic format. The Sequence Listing is provided as a file entitled “2017-02-14_01146-0039-00US_Sequence_Listing_ST25.txt” created on Feb. 14, 2017, which is 76,260 bytes in size. The information in the electronic format of the sequence listing is incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to immunoconjugates comprising anti-HER2 antibodies and methods of using the same.

BACKGROUND

Breast cancer is a highly significant cause of morbidity and mortality worldwide. There are over 1.3 million cases of breast cancer diagnosed globally each year with more than 450,000 deaths related to the disease (Jemal A, Bray F, Center M, et al. Global cancer statistics. CA Cancer J Clin, 2011; 61(2):69-90).

The HER2 (ErbB2) receptor tyrosine kinase is a member of the epidermal growth factor receptor (EGFR) family of transmembrane receptors. Overexpression of HER2 is observed in approximately 20% of human breast cancers and is implicated in the aggressive growth and poor clinical outcomes associated with these tumors (Slamon et al (1987) Science 235:177-182). HER2 protein overexpression can be determined using an immunohistochemistry based assessment of fixed tumor blocks (Press M F, et al (1993) Cancer Res 53:4960-70).

Trastuzumab (CAS 180288-69-1, HERCEPTIN®, huMAb4D5-8, rhuMAb HER2, Genentech) is a recombinant DNA-derived, IgG1 kappa, monoclonal antibody that is a humanized version of a murine anti-HER2 antibody (4D5) that selectively binds with high affinity in a cell-based assay (Kd=5 nM) to the extracellular domain of HER2 (U.S. Pat. No. 5,677,171; U.S. Pat. No. 5,821,337; U.S. Pat. No. 6,054,297; U.S. Pat. No. 6,165,464; U.S. Pat. No. 6,339,142; U.S. Pat. No. 6,407,213; U.S. Pat. No. 6,639,055; U.S. Pat. No. 6,719,971; U.S. Pat. No. 6,800,738; U.S. Pat. No. 7,074,404; Coussens et al (1985) Science 230:1132-9; Slamon et al (1989) Science 244:707-12; Slamon et al (2001) New Engl. J. Med. 344:783-792). Trastuzumab has been shown, in both in vitro assays and in animals, to inhibit the proliferation of human tumor cells that overexpress HER2 (Hudziak et al (1989) Mol Cell Biol 9:1165-72; Lewis et al (1993) Cancer Immunol Immunother; 37:255-63; Baselga et al (1998) Cancer Res. 58:2825-2831). Trastuzumab is a mediator of antibody-dependent cellular cytotoxicity, ADCC (Lewis et al (1993) Cancer Immunol Immunother 37(4):255-263; Hotaling et al (1996) [abstract]. Proc. Annual Meeting Am Assoc Cancer Res; 37:471; Pegram M D, et al (1997) [abstract]. Proc Am Assoc Cancer Res; 38:602; Sliwkowski et al (1999) Seminars in Oncology 26(4), Suppl 12:60-70; Yarden Y. and Sliwkowski, M. (2001) Nature Reviews: Molecular Cell Biology, Macmillan Magazines, Ltd., Vol. 2:127-137).

HERCEPTIN® was approved in 1998 for the treatment of patients with HER2-overexpressing metastatic breast cancers (Baselga et al, (1996) J. Clin. Oncol. 14:737-744) that have received extensive prior anti-cancer therapy, and has since been used in over 300,000 patients (Slamon D J, et al. N Engl J Med 2001; 344:783-92; Vogel C L, et al. J Clin Oncol 2002; 20:719-26; Marty M, et al. J Clin Oncol 2005; 23:4265-74; Romond E H, et al. T N Engl J Med 2005; 353:1673-84; Piccart-Gebhart M J, et al. N Engl J Med 2005; 353:1659-72; Slamon D, et al. [abstract]. Breast Cancer Res Treat 2006, 100 (Suppl 1): 52). In 2006, the FDA approved HERCEPTIN® (trastuzumab, Genentech Inc.) as part of a treatment regimen containing doxorubicin, cyclophosphamide and paclitaxel for the adjuvant treatment of patients with HER2-positive, node-positive breast cancer.

Trastuzumab-MCC-DM1 (T-DM1, trastuzumab emtansine, ado-trastuzumab emtansine, KADCYLA®), a novel antibody-drug conjugate (ADC) for the treatment of HER2-positive breast cancer, is composed of the cytotoxic agent DM1 (a thiol-containing maytansinoid anti-microtubule agent) conjugated to trastuzumab at lysine side chains via an MCC linker, with an average drug load (drug to antibody ratio) of about 3.5. After binding to HER2 expressed on tumor cells, T-DM1 undergoes receptor-mediated internalization, resulting in intracellular release of cytotoxic catabolites containing DM1 and subsequent cell death.

The U.S. Food and Drug Administration approved ado-trastuzumab emtansine, marketed under the tradename KADCYLA®, on Feb. 22, 2013 for the treatment of patients with HER2-positive, metastatic breast cancer who previously received treatment with trastuzumab and a taxane.

Pertuzumab (also known as recombinant humanized monoclonal antibody 2C4, rhuMAb 2C4, PERJETA®, Genentech, Inc, South San Francisco) represents the first in a new class of agents known as HER dimerization inhibitors (HDI) and functions to inhibit the ability of HER2 to form active heterodimers or homodimers with other HER receptors (such as EGFR/HER1, HER2, HER3 and HER4). See, for example, Harari and Yarden Oncogene 19:6102-14 (2000); Yarden and Sliwkowski. Nat Rev Mol Cell Biol 2:127-37 (2001); Sliwkowski Nat Struct Biol 10:158-9 (2003); Cho et al. Nature 421:756-60 (2003); and Malik et al. Pro Am Soc Cancer Res 44:176-7 (2003)

Pertuzumab blockade of the formation of HER2-HER 3 heterodimers in tumor cells has been demonstrated to inhibit critical cell signaling, which results in reduced tumor proliferation and survival (Agus et al. Cancer Cell 2:127-37 (2002)).

Pertuzumab has been evaluated in Phase II studies in combination with trastuzumab in patients with HER2-positive metastatic breast cancer who have previously received trastuzumab for metastatic disease. One study, conducted by the National cancer Institute (NCI), enrolled 11 patients with previously treated HER2-positive metastatic breast cancer. Two out of the 11 patients exhibited a partial response (PR) (Baselga et al., J Clin Oncol 2007 ASCO Annual Meeting Proceedings; 25:18 S (June 20 Supplement): 1004. The results of a Phase II neoadjuvant study evaluating the effect of a novel combination regimen of pertuzumab and trastuzumab plus chemotherapy (Docetaxel) in women with early-stage HER2-positive breast cancer, presented at the CTRC-AACR San Antonio Breast Cancer Symposium (SABCS), Dec. 8-12, 2010, showed that the two HER2 antibodies plus Docetaxel given in the neoadjuvant setting prior to surgery significantly improved the rate of complete tumor disappearance (pathological complete response rate, pCR, of 45.8 percent) in the breast by more than half compared to trastuzumab plus Docetaxel (pCR of 29.0 percent), p=0.014.

Pertuzumab, marketed under the tradename PERJETA®, was approved in 2012 for the treatment of patients with advanced or late-stage (metastatic) HER2-positive breast cancer. HER2-positive breast cancers have increased amounts of the HER2 protein that contributes to cancer cell growth and survival.

On Sep. 30, 2013, the U.S. Food and Drug Administration granted accelerated approval to PERJETA® (pertuzumab) as part of a complete treatment regimen for patients with early stage breast cancer (EBC) before surgery (neoadjuvant setting). PERJETA® is the first FDA-approved drug for the neoadjuvant treatment of breast cancer.

There is a need in the art for additional safe and effective agents that target HER2 for treatment of HER2-associated conditions, such as breast cancer, for use in monotherapy and combination therapy. The invention fulfills that need and provides other benefits.

SUMMARY

The invention provides immunoconjugates comprising anti-HER2 antibodies and methods of using the same.

In some embodiments, an immunoconjugate is provided, which comprises an antibody and a cytotoxic agent, wherein the cytotoxic agent is a center-linked pyrrolobenzodiazepine. In some embodiments, the immunoconjugate has the formula Ab-(L-D)p, wherein:

a) Ab is the antibody of any one of claims 1 to 16;

b) L is a linker;

c) D is a center-linked pyrrolobenzodiazepine; and

d) p ranges from 1-8.

In some embodiments, L-D is of Formula A:

wherein:

R² is

where R^(36a) and R^(36b) are independently selected from H, F, C₁₋₄ saturated alkyl, C₂₋₃ alkenyl, which alkyl and alkenyl groups are optionally substituted by a group selected from C₁₋₄ alkyl amido and C₁₋₄ alkyl ester; or, when one of R^(36a) and R^(36b) is H, the other is selected from nitrile and a C₁₋₄ alkyl ester;

R⁶ and R⁹ are independently selected from H, R, OH, OR, SH, SR, NH₂, NHR, NRR′, NO₂, Me₃Sn and halo;

R⁷ is independently selected from H, R, OH, OR, SH, SR, NH₂, NHR, NRR′, NO₂, Me₃Sn and halo;

Y has the formula:

G is a linker connected to the antibody;

n is an integer selected in the range of 0 to 48;

R^(A4) is a C₁₋₆ alkylene group;

either:

-   -   (a) R¹⁰ is H, and R¹¹ is OH, OR^(A), where R^(A) is C₁₋₄ alkyl;         or     -   (b) R¹⁰ and R¹¹ form a nitrogen-carbon double bond between the         nitrogen and carbon atoms to which they are bound; or     -   (c) R¹⁰ is H and R¹¹ is OSO_(z)M, where z is 2 or 3 and M is a         monovalent pharmaceutically acceptable cation;

R and R′ are each independently selected from optionally substituted C₁₋₁₂ alkyl, C₃₋₂₀ heterocyclyl and C₅₋₂₀ aryl groups, and optionally in relation to the group NRR′, R and R′ together with the nitrogen atom to which they are attached form an optionally substituted 4-, 5-, 6- or 7-membered heterocyclic ring;

R¹⁶, R¹⁷, R¹⁹, R²⁰, R²¹ and R²² are as defined for R⁶, R⁷, R⁹, R¹⁰, R¹¹ and R² respectively;

Z is CH or N;

T and T′ are independently selected from a single bond or a C₁₋₉ alkylene, which chain may be interrupted by one or more heteroatoms, e.g., O, S, N(H), NMe, provided that the number of atoms in the shortest chain of atoms between X and X′ is 3 to 12 atoms; and

X and X′ are independently selected from O, S and N(H); and

wherein the antibody binds to HER2 and comprises (a) HVR—H1 comprising the amino acid sequence of SEQ ID NO:15; (b) HVR—H2 comprising the amino acid sequence of SEQ ID NO:16; (c) HVR—H3 comprising the amino acid sequence of SEQ ID NO:17; (d) HVR-L1 comprising the amino acid sequence of SEQ ID NO:12; (e) HVR-L2 comprising the amino acid sequence of SEQ ID NO:13; and (f) HVR-L3 comprising the amino acid sequence of SEQ ID NO:14. In some embodiments, the antibody comprises a heavy chain variable region comprising the sequence of SEQ ID NO: 11 and a light chain variable region comprising the sequence of SEQ ID NO: 10. In some embodiments, the antibody is a monoclonal antibody. In some embodiments, the antibody is a humanized or chimeric antibody. In some embodiments, the antibody is an antibody fragment that binds HER2.

In some embodiments, HER2 is human HER2 comprising amino acids 23 to 1255 of SEQ ID NO: 1. In some embodiments, the antibody binds to extracellular domain I of HER2. In some embodiments, extracellular domain I of HER2 has the sequence of SEQ ID NO: 35. In some embodiments, the antibody binds to loop 163-189 and loop 185-189 of extracellular domain I (e.g., a first loop defined by amino acids 163-189 and a second loop defined by amino acids 185-189 of extracellular domain I). In some embodiments, the antibody contacts His171, Ser186, Ser187 and Glu188 of extracellular domain I.

In some embodiments, the antibody is an IgG1, IgG2a or IgG2b antibody. In any of the embodiments described herein, the antibody may comprise one or more engineered free cysteine amino acids residues. In any of the embodiments described herein, the one or more engineered free cysteine amino acids residues may be located in the heavy chain. In any of the embodiments described herein, the one or more engineered free cysteine amino acids residues may be located in the light chain. In some embodiments, the antibody comprises at least one mutation in the heavy chain constant region selected from A118C and S400C. In some embodiments, the antibody comprises at least one mutation in the light chain constant region selected from K149C and V205C.

In some embodiments, the antibody comprises:

-   -   a) a heavy chain comprising the sequence of SEQ ID NO: 19 and a         light chain comprising the sequence of SEQ ID NO: 18; or     -   b) a heavy chain comprising the sequence of SEQ ID NO: 19 and a         light chain comprising the sequence of SEQ ID NO: 23; or     -   c) a heavy chain comprising the sequence of SEQ ID NO: 24 and a         light chain comprising the sequence of SEQ ID NO: 18.         In some embodiments, the antibody comprises the heavy chain         constant region of SEQ ID NO: 28. In some embodiments, the         antibody comprises the light chain constant region of SEQ ID NO:         25.

In some embodiments, the immunoconjugate comprises an antibody that binds to HER2, wherein the antibody comprises a heavy chain comprising the sequence of SEQ ID NO: 19 and a light chain comprising the sequence of SEQ ID NO: 23. In some embodiments, an isolated antibody that binds to HER2 is provided, wherein the antibody comprises a heavy chain comprising the sequence of SEQ ID NO: 24 and a light chain comprising the sequence of SEQ ID NO: 18.

In some embodiments of the immunoconjugate, R⁹ is H. In some embodiments, R⁶ is H. In some embodiments, R⁷ is OR^(7A), where R^(7A) is optionally substituted C₁₋₄ alkyl. In some embodiments, R^(7A) is Me. In some embodiments, X is O. In some embodiments, T is selected from a single bond, C₁, and a C₂ alkylene group. In some embodiments, T is a C₁ alkylene group. In some embodiments, R^(36a) and R^(36b) are both H. In some embodiments, R^(36a) and R^(36b) are both methyl. In some embodiments, one of R^(36a) and R^(36b) is H, and the other is selected from C₁₋₄ saturated alkyl, C₂₋₃ alkenyl, which alkyl and alkenyl groups are optionally substituted. In some embodiments, the group of R^(36a) and R^(36b) which is not H is selected from methyl and ethyl. In some embodiments, R¹⁰ is H, and R¹¹ is OH. In some embodiments, R¹⁰ and R¹¹ form a nitrogen-carbon double bond between the nitrogen and carbon atoms to which they are bound. In some embodiments, R¹⁶, R¹⁷, R¹⁹, R²⁰, R²¹, R²², X′ and T′ are the same as R⁶, R⁷, R⁹, R¹⁰, R², X and T, respectively.

In some embodiments, an immunoconjugate comprises the structure:

wherein Y is defined as above. In some embodiments, the immunoconjugate comprises the structure:

wherein Ab is an antibody that binds HER2 described herein.

In any of the immunoconjugates described herein, p may range from 1.3-2, 1.4-2, 1.5-2, or 2-5.

In some embodiments, a pharmaceutical formulation is provided, comprising an immunoconjugate described herein and a pharmaceutically acceptable carrier. In some embodiments, the pharmaceutical formulation further comprises an additional therapeutic agent. In some embodiments, the additional therapeutic agent is an antibody or immunoconjugate that binds to HER2. In some embodiments, the additional therapeutic agent is (i) an antibody or immunoconjugate that binds to domain II of HER2, and/or (ii) an antibody or immunoconjugate that binds to domain IV or HER2. In some embodiments, the additional therapeutic agent is (i) an antibody or immunoconjugate that binds to epitope 2C4, and/or (ii) an antibody or immunoconjugate that binds to epitope 4D5. In some embodiments, the additional therapeutic agent is selected from trastuzumab, trastuzumab-MCC-DM1 (T-DM1), and pertuzumab. In some embodiments, the pharmaceutical formulation further comprises (1) trastuzumab or T-DM1, and (2) pertuzumab.

In some embodiments, methods of treating an individual having a HER2-positive cancer are provided. In some embodiments, a method comprises administering to the individual an effective amount of an immunoconjugate described herein, or a pharmaceutical composition described herein. In some embodiments, the HER2-positive cancer is breast cancer or gastric cancer. In some embodiments, the HER2-positive breast cancer is early-stage breast cancer. In some embodiments, the HER2-positive breast cancer is metastatic breast cancer. In some embodiments, the HER2-positive cancer is recurrent cancer. In some embodiments, the recurrent cancer is locally recurrent cancer. In some embodiments, the HER2-positive cancer is advanced cancer. In some embodiments, the HER2-positive cancer is non-resectable. In some embodiments, the method further comprises administering an additional therapeutic agent to the individual.

In some embodiments, a method of treating an individual having a HER2-positive cancer comprises administering to the individual an effective amount of an immunoconjugate described herein and at least one additional therapeutic agent to the individual. In some embodiments, the additional therapeutic agent is an antibody or immunoconjugate that binds to HER2. In some embodiments, the additional therapeutic agent is (i) an antibody or immunoconjugate that binds to domain II of HER2, and/or (ii) an antibody or immunoconjugate that binds to domain IV or HER2. In some embodiments, the additional therapeutic agent is (i) an antibody or immunoconjugate that binds to epitope 2C4, and/or (ii) an antibody or immunoconjugate that binds to epitope 4D5. In some embodiments, the additional therapeutic agent is selected from trastuzumab, trastuzumab-MCC-DM1 (T-DM1), and pertuzumab. In some embodiments, the additional therapeutic agents are (1) trastuzumab or T-DM1, and (2) pertuzumab. In some embodiments, the HER2-positive cancer is breast cancer or gastric cancer. In some embodiments, the HER2-positive breast cancer is early-stage breast cancer. In some embodiments, the HER2-positive breast cancer is metastatic breast cancer. In some embodiments, the HER2-positive cancer is recurrent cancer. In some embodiments, the recurrent cancer is locally recurrent cancer. In some embodiments, the HER2-positive cancer is advanced cancer. In some embodiments, the HER2-positive cancer is non-resectable.

In some embodiments, a method of treating an individual having a HER2-positive cancer comprises:

-   -   a) subjecting the individual to neoadjuvant treatment with an         immunoconjugate described herein or a pharmaceutical formulation         described herein,     -   b) removing the cancer by definitive surgery, and     -   c) subjecting the individual to adjuvant treatment with an         immunoconjugate described herein or a pharmaceutical formulation         described herein.         In some embodiments, the HER2-positive cancer is breast cancer         or gastric cancer.

In some embodiments, methods of inhibiting proliferation of a HER2-positive cell are provided. In some embodiments a method comprises exposing the cell to an immunoconjugate described herein under conditions permissive for binding of the immunoconjugate to HER2 on the surface of the cell, thereby inhibiting proliferation of the cell. In some embodiments, the cell is a breast cancer cell of a gastric cancer cell.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows an alignment of the human VH subgroup I (VH₁) consensus sequence and heavy chain variable region sequences of murine 7C2.B9 (“7C2”) and humanized 7C2.v2.2.LA, as described in Example 1.

FIG. 2 shows an alignment of the human VL kappa IV (VL_(KIV)) consensus sequence and light chain variable region sequences of murine 7C2.B9 (“7C2”) and humanized 7C2.v2.2.LA, as described in Example 1.

FIG. 3 shows the Her2 extracellular domain structure, with domains I to IV indicated, and the domains to which anti-Her2 antibodies trastuzumab, pertuzumab, and 7C2 bind.

FIG. 4 shows change in tumor volume (mm3) over time upon treatment with hu7C2.v2.2.LA antibody-drug conjugates (ADCs), as described in Example 3.

FIG. 5 shows change in tumor volume (mm3) over time upon treatment with hu7C2.v2.2.LA antibody-drug conjugates (ADCs), as described in Example 4.

FIG. 6 show the structures for certain antibody-drug conjugates used in the examples herein.

FIGS. 7A-B show the pertuzumab main species antibody light chain (A) and heavy chain (B) amino acid sequences.

FIGS. 8A-B show exemplary pertuzumab variant species antibody light chain (A) and heavy chain (B) amino acid sequences.

FIGS. 9A-B show the trastuzumab antibody light chain (A) and heavy chain (B) amino acid sequences.

FIG. 10 shows a schematic of the Her2 receptor and the sequences for domains I to IV.

FIGS. 11A-D show (A) crystal structure of the complex between HER2 ECD (surface shaded by domain and shown as a space-filling model) and 7C2 Fab. The 7C2 Fab binds to domain I of HER2, which is different from the binding epitopes of the trastuzumab Fab (Tmab, PDB code: 1N8Z) and the pertuzumab Fab (Pmab, PDB code: 1S78). (B) Superposition of the structures of HER2 ECD within the trastuzumab/HER2 complex, pertuzumab/HER2 complex, and 7C2/HER2 complex. (C) The 7C2/HER2 complex interface. The side chains of the residues involved in the 7C2/HER2 interaction are shown as sticks. Some of the potential intermolecular hydrogen bonds are shown as dashed lines. (D) The 7C2 binding epitope is partially overlapped with the chA21 single-chain Fv (scFv). Superposition of the structure of the chA21 scFv/HER2 complex (PDB code: 3H3B) with the 7C2/HER2 complex.

DETAILED DESCRIPTION

Reference will now be made in detail to certain embodiments of the invention, examples of which are illustrated in the accompanying structures and formulas. While the invention will be described in conjunction with the enumerated embodiments, it will be understood that they are not intended to limit the invention to those embodiments. On the contrary, the invention is intended to cover all alternatives, modifications, and equivalents which may be included within the scope of the present invention as defined by the claims. One skilled in the art will recognize many methods and materials similar or equivalent to those described herein, which could be used in the practice of the present invention. The present invention is in no way limited to the methods and materials described.

All references cited throughout the disclosure are expressly incorporated by reference herein in their entirety. In the event that one or more of the incorporated literature, patents, and similar materials differs from or contradicts this application, including but not limited to defined terms, term usage, described techniques, or the like, this application controls.

I. Definitions

The words “comprise,” “comprising,” “include,” “including,” and “includes” when used in this specification and claims are intended to specify the presence of stated features, integers, components, or steps, but they do not preclude the presence or addition of one or more other features, integers, components, steps, or groups thereof.

An “acceptor human framework” for the purposes herein is a framework comprising the amino acid sequence of a light chain variable domain (VL) framework or a heavy chain variable domain (VH) framework derived from a human immunoglobulin framework or a human consensus framework, as defined below. An acceptor human framework “derived from” a human immunoglobulin framework or a human consensus framework may comprise the same amino acid sequence thereof, or it may contain amino acid sequence changes. In some embodiments, the number of amino acid changes are 10 or less, 9 or less, 8 or less, 7 or less, 6 or less, 5 or less, 4 or less, 3 or less, or 2 or less. In some embodiments, the VL acceptor human framework is identical in sequence to the VL human immunoglobulin framework sequence or human consensus framework sequence.

“Affinity” refers to the strength of the sum total of noncovalent interactions between a single binding site of a molecule (e.g., an antibody) and its binding partner (e.g., an antigen). Unless indicated otherwise, as used herein, “binding affinity” refers to intrinsic binding affinity which reflects a 1:1 interaction between members of a binding pair (e.g., antibody and antigen). The affinity of a molecule X for its partner Y can generally be represented by the dissociation constant (Kd). Affinity can be measured by common methods known in the art, including those described herein. Specific illustrative and exemplary embodiments for measuring binding affinity are described in the following.

An “affinity matured” antibody refers to an antibody with one or more alterations in one or more hypervariable regions (HVRs), compared to a parent antibody which does not possess such alterations, such alterations resulting in an improvement in the affinity of the antibody for antigen.

The terms “anti-HER2 antibody” and “an antibody that binds to HER2” refer to an antibody that is capable of binding HER2 with sufficient affinity such that the antibody is useful as a diagnostic and/or therapeutic agent in targeting HER2. In one embodiment, the extent of binding of an anti-HER2 antibody to an unrelated, non-HER2 protein is less than about 10% of the binding of the antibody to HER2 as measured, e.g., by a radioimmunoassay (RIA). In certain embodiments, an antibody that binds to HER2 has a dissociation constant (Kd) of ≦1 μM, ≦100 nM, ≦10 nM, ≦5 nm, ≦4 nM, ≦3 nM, ≦2 nM, ≦1 nM, ≦0.1 nM, ≦0.01 nM, or ≦0.001 nM (e.g., 10⁻⁸ M or less, e.g. from 10⁻⁸M to 10⁻¹³M, e.g., from 10⁻⁹M to 10⁻¹³ M). In certain embodiments, an anti-HER2 antibody binds to an epitope of HER2 that is conserved among HER2 from different species.

The term “antibody” is used herein in the broadest sense and encompasses various antibody structures, including but not limited to monoclonal antibodies, polyclonal antibodies, multispecific antibodies (e.g., bispecific antibodies), and antibody fragments so long as they exhibit the desired antigen-binding activity.

An “antibody fragment” refers to a molecule other than an intact antibody that comprises a portion of an intact antibody and that binds the antigen to which the intact antibody binds. Examples of antibody fragments include but are not limited to Fv, Fab, Fab′, Fab′-SH, F(ab′)₂; diabodies; linear antibodies; single-chain antibody molecules (e.g. scFv); and multispecific antibodies formed from antibody fragments.

An “antibody that binds to the same epitope” as a reference antibody refers to an antibody that blocks binding of the reference antibody to its antigen in a competition assay by 50% or more, and conversely, the reference antibody blocks binding of the antibody to its antigen in a competition assay by 50% or more. An exemplary competition assay is provided herein.

The terms “cancer” and “cancerous” refer to or describe the physiological condition in mammals that is typically characterized by unregulated cell growth/proliferation. Examples of cancer include, but are not limited to, carcinoma, lymphoma, blastoma, sarcoma, and leukemia. In some embodiments, the cancer is breast cancer or gastric cancer. In some embodiments, a cancer is any HER2-positive cancer.

A “HER2-positive” cancer comprises cancer cells which have higher than normal levels of HER2. Examples of HER2-positive cancer include HER2-positive breast cancer and HER2-positive gastric cancer. Optionally, HER2-positive cancer has an immunohistochemistry (IHC) score of 2+ or 3+ and/or an in situ hybridization (ISH) amplification ratio ≧2.0.

The term “early stage breast cancer (EBC)” or “early breast cancer” is used herein to refer to breast cancer that has not spread beyond the breast or the axillary lymph nodes. This includes ductal carcinoma in situ and stage I, stage IIA, stage IIB, and stage IIIA breast cancers.

Reference to a tumor or cancer as a “Stage 0,” “Stage I,” “Stage II,” “Stage III,” or “Stage IV”, and various sub-stages within this classification, indicates classification of the tumor or cancer using the Overall Stage Grouping or Roman Numeral Staging methods known in the art. Although the actual stage of the cancer is dependent on the type of cancer, in general, a Stage 0 cancer is an in situ lesion, a Stage I cancer is small localized tumor, a Stage II and III cancer is a local advanced tumor which exhibits involvement of the local lymph nodes, and a Stage IV cancer represents metastatic cancer. The specific stages for each type of tumor is known to the skilled clinician.

The term “metastatic breast cancer” means the state of breast cancer where the cancer cells are transmitted from the original site to one or more sites elsewhere in the body, by the blood vessels or lymphatics, to form one or more secondary tumors in one or more organs besides the breast.

An “advanced” cancer is one which has spread outside the site or organ of origin, either by local invasion or metastasis. Accordingly, the term “advanced” cancer includes both locally advanced and metastatic disease.

A “recurrent” cancer is one which has regrown, either at the initial site or at a distant site, after a response to initial therapy, such as surgery.

A “locally recurrent” cancer is cancer that returns after treatment in the same place as a previously treated cancer.

An “operable” or “resectable” cancer is cancer which is confined to the primary organ and suitable for surgery (resection).

A “non-resectable” or “unresectable” cancer is not able to be removed (resected) by surgery.

The term “chimeric” antibody refers to an antibody in which a portion of the heavy and/or light chain is derived from a particular source or species, while the remainder of the heavy and/or light chain is derived from a different source or species.

The “class” of an antibody refers to the type of constant domain or constant region possessed by its heavy chain. There are five major classes of antibodies: IgA, IgD, IgE, IgG, and IgM, and several of these may be further divided into subclasses (isotypes), e.g., IgG₁, IgG₂, IgG₃, IgG₄, IgA₁, and IgA₂. The heavy chain constant domains that correspond to the different classes of immunoglobulins are called α, δ, ε, γ, and μ, respectively.

The term “cytotoxic agent” as used herein refers to a substance that inhibits or prevents a cellular function and/or causes cell death or destruction. Cytotoxic agents include, but are not limited to, radioactive isotopes (e.g., At²¹¹, I¹³¹, I¹²⁵, Y⁹⁰, Re¹⁸⁶, Re¹⁸⁸, sm¹⁵³, Bi²¹², P³², Pb²¹² and radioactive isotopes of Lu); chemotherapeutic agents or drugs (e.g., methotrexate, adriamicin, vinca alkaloids (vincristine, vinblastine, etoposide), doxorubicin, melphalan, mitomycin C, chlorambucil, daunorubicin or other intercalating agents); growth inhibitory agents; enzymes and fragments thereof such as nucleolytic enzymes; antibiotics; toxins such as small molecule toxins or enzymatically active toxins of bacterial, fungal, plant or animal origin, including fragments and/or variants thereof; and the various antitumor or anticancer agents disclosed below.

“Effector functions” refer to those biological activities attributable to the Fc region of an antibody, which vary with the antibody isotype. Examples of antibody effector functions include: C1q binding and complement dependent cytotoxicity (CDC); Fc receptor binding; antibody-dependent cell-mediated cytotoxicity (ADCC); phagocytosis; down regulation of cell surface receptors (e.g. B cell receptor); and B cell activation.

An “effective amount” of an agent, e.g., a pharmaceutical formulation, refers to an amount effective, at dosages and for periods of time necessary, to achieve the desired therapeutic or prophylactic result. The effective amount of the drug for treating cancer may reduce the number of cancer cells; reduce the tumor size; inhibit (i.e., slow to some extent and preferably stop) cancer cell infiltration into peripheral organs; inhibit (i.e., slow to some extent and preferably stop) tumor metastasis; inhibit, to some extent, tumor growth; and/or relieve to some extent one or more of the symptoms associated with the cancer. To the extent the drug may prevent growth and/or kill existing cancer cells, it may be cytostatic and/or cytotoxic. The effective amount may extend progression free survival (e.g. as measured by Response Evaluation Criteria for Solid Tumors, RECIST, or CA-125 changes), result in an objective response (including a partial response, PR, or complete response, CR), increase overall survival time, and/or improve one or more symptoms of cancer (e.g. as assessed by FOSI).

The term “epitope” refers to the particular site on an antigen molecule to which an antibody binds.

The “epitope 4D5” or “4D5 epitope” or “4D5” is the region in the extracellular domain of HER2 to which the antibody 4D5 (ATCC CRL 10463) and trastuzumab bind. This epitope is close to the transmembrane domain of HER2, and within domain IV of HER2. To screen for antibodies which bind to the 4D5 epitope, a routine cross-blocking assay such as that described in Antibodies, A Laboratory Manual, Cold Spring Harbor Laboratory, Ed Harlow and David Lane (1988), can be performed. Alternatively, epitope mapping can be performed to assess whether the antibody binds to the 4D5 epitope of HER2 (e.g. any one or more residues in the region from about residue 550 to about residue 610, inclusive, of HER2 (SEQ ID NO: 39).

The “epitope 2C4” or “2C4 epitope” is the region in the extracellular domain of HER2 to which the antibody 2C4 binds. In order to screen for antibodies which bind to the 2C4 epitope, a routine cross-blocking assay such as that described in Antibodies, A Laboratory Manual, Cold Spring Harbor Laboratory, Ed Harlow and David Lane (1988), can be performed. Alternatively, epitope mapping can be performed to assess whether the antibody binds to the 2C4 epitope of HER2. Epitope 2C4 comprises residues from domain II in the extracellular domain of HER2. The 2C4 antibody and pertuzumab bind to the extracellular domain of HER2 at the junction of domains I, II and III (Franklin et al. Cancer Cell 5:317-328 (2004)).

The term “Fc region” herein is used to define a C-terminal region of an immunoglobulin heavy chain that contains at least a portion of the constant region. The term includes native sequence Fc regions and variant Fc regions. In one embodiment, a human IgG heavy chain Fc region extends from Cys226, or from Pro230, to the carboxyl-terminus of the heavy chain. However, the C-terminal lysine (Lys447) of the Fc region may or may not be present. Unless otherwise specified herein, numbering of amino acid residues in the Fc region or constant region is according to the EU numbering system, also called the EU index, as described in Kabat et al., Sequences of Proteins of Immunological Interest, 5th Ed. Public Health Service, National Institutes of Health, Bethesda, Md., 1991.

“Framework” or “FR” refers to variable domain residues other than hypervariable region (HVR) residues. The FR of a variable domain generally consists of four FR domains: FR1, FR2, FR3, and FR4. Accordingly, the HVR and FR sequences generally appear in the following sequence in VH (or VL): FR1-H1(L1)-FR2-H2(L2)-FR3-H3(L3)-FR4.

The terms “full length antibody,” “intact antibody,” and “whole antibody” are used herein interchangeably to refer to an antibody having a structure substantially similar to a native antibody structure or having heavy chains that contain an Fc region as defined herein.

The term “glycosylated forms of HER2” refers to naturally occurring forms of HER2 that are post-translationally modified by the addition of carbohydrate residues.

The terms “host cell,” “host cell line,” and “host cell culture” are used interchangeably and refer to cells into which exogenous nucleic acid has been introduced, including the progeny of such cells. Host cells include “transformants” and “transformed cells,” which include the primary transformed cell and progeny derived therefrom without regard to the number of passages. Progeny may not be completely identical in nucleic acid content to a parent cell, but may contain mutations. Mutant progeny that have the same function or biological activity as screened or selected for in the originally transformed cell are included herein.

A “human antibody” is one which possesses an amino acid sequence which corresponds to that of an antibody produced by a human or a human cell or derived from a non-human source that utilizes human antibody repertoires or other human antibody-encoding sequences. This definition of a human antibody specifically excludes a humanized antibody comprising non-human antigen-binding residues.

A “human consensus framework” is a framework which represents the most commonly occurring amino acid residues in a selection of human immunoglobulin VL or VH framework sequences. Generally, the selection of human immunoglobulin VL or VH sequences is from a subgroup of variable domain sequences. Generally, the subgroup of sequences is a subgroup as in Kabat et al., Sequences of Proteins of Immunological Interest, Fifth Edition, NIH Publication 91-3242, Bethesda Md. (1991), vols. 1-3. In one embodiment, for the VL, the subgroup is subgroup kappa I as in Kabat et al., supra. In one embodiment, for the VH, the subgroup is subgroup III as in Kabat et al., supra.

A “humanized” antibody refers to a chimeric antibody comprising amino acid residues from non-human HVRs and amino acid residues from human FRs. In certain embodiments, a humanized antibody will comprise substantially all of at least one, and typically two, variable domains, in which all or substantially all of the HVRs (e.g., CDRs) correspond to those of a non-human antibody, and all or substantially all of the FRs correspond to those of a human antibody. A humanized antibody optionally may comprise at least a portion of an antibody constant region derived from a human antibody. A “humanized form” of an antibody, e.g., a non-human antibody, refers to an antibody that has undergone humanization.

The term “hypervariable region” or “HVR,” as used herein, refers to each of the regions of an antibody variable domain which are hypervariable in sequence and/or form structurally defined loops (“hypervariable loops”). Generally, native four-chain antibodies comprise six HVRs; three in the VH (H1, H2, H3), and three in the VL (L1, L2, L3). HVRs generally comprise amino acid residues from the hypervariable loops and/or from the “complementarity determining regions” (CDRs), the latter being of highest sequence variability and/or involved in antigen recognition. Exemplary hypervariable loops occur at amino acid residues 26-32 (L1), 50-52 (L2), 91-96 (L3), 26-32 (H1), 53-55 (H2), and 96-101 (H3). (Chothia and Lesk, J. Mol. Biol. 196:901-917 (1987).) Exemplary CDRs (CDR-L1, CDR-L2, CDR-L3, CDR-H1, CDR-H2, and CDR-H3) occur at amino acid residues 24-34 of L1, 50-56 of L2, 89-97 of L3, 31-35B of H1, 50-65 of H2, and 95-102 of H3. (Kabat et al., Sequences of Proteins of Immunological Interest, 5th Ed. Public Health Service, National Institutes of Health, Bethesda, Md. (1991).) With the exception of CDR1 in VH, CDRs generally comprise the amino acid residues that form the hypervariable loops. CDRs also comprise “specificity determining residues,” or “SDRs,” which are residues that contact antigen. SDRs are contained within regions of the CDRs called abbreviated-CDRs, or a-CDRs. Exemplary a-CDRs (a-CDR-L1, a-CDR-L2, a-CDR-L3, a-CDR-H1, a-CDR-H2, and a-CDR-H3) occur at amino acid residues 31-34 of L1, 50-55 of L2, 89-96 of L3, 31-35B of H1, 50-58 of H2, and 95-102 of H3. (See Almagro and Fransson, Front. Biosci. 13:1619-1633 (2008).) Unless otherwise indicated, HVR residues and other residues in the variable domain (e.g., FR residues) are numbered herein according to Kabat et al., supra.

An “immunoconjugate” is an antibody conjugated to one or more heterologous molecule(s), including but not limited to a cytotoxic agent.

A “patient” or “individual” or “subject” is a mammal. Mammals include, but are not limited to, domesticated animals (e.g., cows, sheep, cats, dogs, and horses), primates (e.g., humans and non-human primates such as monkeys), rabbits, and rodents (e.g., mice and rats). In certain embodiments, the patient, individual, or subject is a human. In some embodiments, the patient may be a “cancer patient,” i.e. one who is suffering or at risk for suffering from one or more symptoms of cancer, in particular gastric or breast cancer.

A “patient population” refers to a group of cancer patients. Such populations can be used to demonstrate statistically significant efficacy and/or safety of a drug.

A “relapsed” patient is one who has signs or symptoms of cancer after remission. Optionally, the patient has relapsed after adjuvant or neoadjuvant therapy.

A cancer or biological sample which “displays HER expression, amplification, or activation” is one which, in a diagnostic test, expresses (including overexpresses) a HER receptor, has amplified HER gene, and/or otherwise demonstrates activation or phosphorylation of a HER receptor.

“Neoadjuvant therapy” or “preoperative therapy” herein refers to therapy given prior to surgery. The goal of neoadjuvant therapy is to provide immediate systemic treatment, potentially eradicating micrometastases that would otherwise proliferate if the standard sequence of surgery followed by systemic therapy were followed. Neoadjuvant therapy may also help to reduce tumor size thereby allowing complete resection of initially unresectable tumors or preserving portions of the organ and its functions. Furthermore, neoadjuvant therapy permits an in vivo assessment of drug efficacy, which may guide the choice of subsequent treatments.

“Adjuvant therapy” herein refers to therapy given after definitive surgery, where no evidence of residual disease can be detected, so as to reduce the risk of disease recurrence. The goal of adjuvant therapy is to prevent recurrence of the cancer, and therefore to reduce the chance of cancer-related death. Adjuvant therapy herein specifically excludes neoadjuvant therapy.

“Definitive surgery” is used as that term is used within the medical community. Definitive surgery includes, for example, procedures, surgical or otherwise, that result in removal or resection of the tumor, including those that result in the removal or resection of all grossly visible tumor. Definitive surgery includes, for example, complete or curative resection or complete gross resection of the tumor. Definitive surgery includes procedures that occur in one or more stages, and includes, for example, multi-stage surgical procedures where one or more surgical or other procedures are performed prior to resection of the tumor. Definitive surgery includes procedures to remove or resect the tumor including involved organs, parts of organs and tissues, as well as surrounding organs, such as lymph nodes, parts of organs, or tissues. Removal may be incomplete such that tumor cells might remain even though undetected.

“Survival” refers to the patient remaining alive, and includes disease free survival (DFS), progression free survival (PFS) and overall survival (OS). Survival can be estimated by the Kaplan-Meier method, and any differences in survival are computed using the stratified log-rank test.

“Progression-Free Survival” (PFS) is the time from the first day of treatment to documented disease progression (including isolated CNS progression) or death from any cause on study, whichever occurs first.

“Disease free survival (DFS)” refers to the patient remaining alive, without return of the cancer, for a defined period of time such as about 1 year, about 2 years, about 3 years, about 4 years, about 5 years, about 10 years, etc., from initiation of treatment or from initial diagnosis. In one aspect, DFS is analyzed according to the intent-to-treat principle, i.e., patients are evaluated on the basis of their assigned therapy. The events used in the analysis of DFS can include local, regional and distant recurrence of cancer, occurrence of secondary cancer, and death from any cause in patients without a prior event (e.g, breast cancer recurrence or second primary cancer).

“Overall survival” refers to the patient remaining alive for a defined period of time, such as about 1 year, about 2 years, about 3 years, about 4 years, about 5 years, about 10 years, etc., from initiation of treatment or from initial diagnosis. In the studies underlying the invention the event used for survival analysis was death from any cause.

By “extending survival” is meant increasing DFS and/or OS in a treated patient relative to an untreated patient, or relative to a control treatment protocol. Survival is monitored for at least about six months, or at least about 1 year, or at least about 2 years, or at least about 3 years, or at least about 4 years, or at least about 5 years, or at least about 10 years, etc., following the initiation of treatment or following the initial diagnosis.

By “monotherapy” is meant a therapeutic regimen that includes only a single therapeutic agent for the treatment of the cancer or tumor during the course of the treatment period.

By “maintenance therapy” is meant a therapeutic regimen that is given to reduce the likelihood of disease recurrence or progression. Maintenance therapy can be provided for any length of time, including extended time periods up to the life-span of the subject. Maintenance therapy can be provided after initial therapy or in conjunction with initial or additional therapies. Dosages used for maintenance therapy can vary and can include diminished dosages as compared to dosages used for other types of therapy.

As defined herein, the terms “trastuzumab”, “HERCEPTIN®” and “huMAb4D5-8” are used interchangeably. Such antibody preferably comprises the light and heavy chain amino acid sequences shown in SEQ ID NO: 30 and SEQ ID NO. 29, respectively.

For the purposes herein, “pertuzumab”, “PERJETA®” and “rhuMAb 2C4”, are used interchangeably. Such antibody comprises a main species antibody having the light and heavy chain amino acid sequences in SEQ ID NOs: 32 and 31, respectively (FIGS. 7A and B). In some embodiments, pertuzumab comprises a variant species antibody with an amino-terminal leader extension, e.g., comprising a light chain amino acid sequence of SEQ ID NO: 34, and a heavy chain amino acid sequence of SEQ ID NO: 33. The antibody is optionally produced by recombinant Chinese Hamster Ovary (CHO) cells.

As defined herein, the terms “T-DM1,” “trastuzumab-MCC-DM1,” “ado-trastuzumab emtansine,” “trastuzumab emtansine,” and “KADCYLA®” are used interchangeably, and refer to trastuzumab linked through the linker moiety MCC to the maytansinoid drug moiety DM1, including all mixtures of variously loaded and attached antibody-drug conjugates where 1, 2, 3, 4, 5, 6, 7, and 8 drug moieties are covalently attached to the antibody trastuzumab (U.S. Pat. No. 7,097,840; U.S. Pat. No. 8,337,856; US 2005/0276812; US 2005/0166993).

An “isolated antibody” is one which has been separated from a component of its natural environment. In some embodiments, an antibody is purified to greater than 95% or 99% purity as determined by, for example, electrophoretic (e.g., SDS-PAGE, isoelectric focusing (IEF), capillary electrophoresis) or chromatographic (e.g., ion exchange or reverse phase HPLC). For review of methods for assessment of antibody purity, see, e.g., Flatman et al., J. Chromatogr. B 848:79-87 (2007).

An “isolated nucleic acid” refers to a nucleic acid molecule that has been separated from a component of its natural environment. An isolated nucleic acid includes a nucleic acid molecule contained in cells that ordinarily contain the nucleic acid molecule, but the nucleic acid molecule is present extrachromosomally or at a chromosomal location that is different from its natural chromosomal location.

“Isolated nucleic acid encoding an anti-HER2 antibody” refers to one or more nucleic acid molecules encoding antibody heavy and light chains (or fragments thereof), including such nucleic acid molecule(s) in a single vector or separate vectors, and such nucleic acid molecule(s) present at one or more locations in a host cell.

The term “HER2,” as used herein, refers to any native, mature HER2 which results from processing of a HER2 precursor protein in a cell. The term includes HER2 from any vertebrate source, including mammals such as primates (e.g. humans and cynomolgus monkeys) and rodents (e.g., mice and rats), unless otherwise indicated. The term also includes naturally occurring variants of HER2, e.g., splice variants or allelic variants. The amino acid sequence of an exemplary human HER2 precursor protein, with signal sequence (with signal sequence, amino acids 1-22) is shown in SEQ ID NO:1. The amino acid sequence of an exemplary mature human HER2 is amino acids 23-1255 of SEQ ID NO: 1.

The term “HER2-positive cell” refers to a cell that expresses HER2 on its surface.

The term “monoclonal antibody” as used herein refers to an antibody obtained from a population of substantially homogeneous antibodies, i.e., the individual antibodies comprising the population are identical and/or bind the same epitope, except for possible variant antibodies, e.g., containing naturally occurring mutations or arising during production of a monoclonal antibody preparation, such variants generally being present in minor amounts. In contrast to polyclonal antibody preparations, which typically include different antibodies directed against different determinants (epitopes), each monoclonal antibody of a monoclonal antibody preparation is directed against a single determinant on an antigen. Thus, the modifier “monoclonal” indicates the character of the antibody as being obtained from a substantially homogeneous population of antibodies, and is not to be construed as requiring production of the antibody by any particular method. For example, the monoclonal antibodies to be used in accordance with the present invention may be made by a variety of techniques, including but not limited to the hybridoma method, recombinant DNA methods, phage-display methods, and methods utilizing transgenic animals containing all or part of the human immunoglobulin loci, such methods and other exemplary methods for making monoclonal antibodies being described herein.

A “naked antibody” refers to an antibody that is not conjugated to a heterologous moiety (e.g., a cytotoxic moiety) or radiolabel. The naked antibody may be present in a pharmaceutical formulation.

“Native antibodies” refer to naturally occurring immunoglobulin molecules with varying structures. For example, native IgG antibodies are heterotetrameric glycoproteins of about 150,000 daltons, composed of two identical light chains and two identical heavy chains that are disulfide-bonded. From N- to C-terminus, each heavy chain has a variable region (VH), also called a variable heavy domain or a heavy chain variable domain, followed by three constant domains (CH1, CH2, and CH3). Similarly, from N- to C-terminus, each light chain has a variable region (VL), also called a variable light domain or a light chain variable domain, followed by a constant light (CL) domain. The light chain of an antibody may be assigned to one of two types, called kappa (κ) and lambda (λ), based on the amino acid sequence of its constant domain.

A “vial” is a container suitable for holding a liquid or lyophilized preparation. In one embodiment, the vial is a single-use vial, e.g. a 20-cc single-use vial with a stopper.

The term “package insert” is used to refer to instructions customarily included in commercial packages of therapeutic products, that contain information about the indications, usage, dosage, administration, combination therapy, contraindications and/or warnings concerning the use of such therapeutic products.

“Percent (%) amino acid sequence identity” with respect to a reference polypeptide sequence is defined as the percentage of amino acid residues in a candidate sequence that are identical with the amino acid residues in the reference polypeptide sequence, after aligning the sequences and introducing gaps, if necessary, to achieve the maximum percent sequence identity, and not considering any conservative substitutions as part of the sequence identity. Alignment for purposes of determining percent amino acid sequence identity can be achieved in various ways that are within the skill in the art, for instance, using publicly available computer software such as BLAST, BLAST-2, ALIGN or Megalign (DNASTAR) software. Those skilled in the art can determine appropriate parameters for aligning sequences, including any algorithms needed to achieve maximal alignment over the full length of the sequences being compared. For purposes herein, however, % amino acid sequence identity values are generated using the sequence comparison computer program ALIGN-2. The ALIGN-2 sequence comparison computer program was authored by Genentech, Inc., and the source code has been filed with user documentation in the U.S. Copyright Office, Washington D.C., 20559, where it is registered under U.S. Copyright Registration No. TXU510087. The ALIGN-2 program is publicly available from Genentech, Inc., South San Francisco, Calif., or may be compiled from the source code. The ALIGN-2 program should be compiled for use on a UNIX operating system, including digital UNIX V4.0D. All sequence comparison parameters are set by the ALIGN-2 program and do not vary.

In situations where ALIGN-2 is employed for amino acid sequence comparisons, the % amino acid sequence identity of a given amino acid sequence A to, with, or against a given amino acid sequence B (which can alternatively be phrased as a given amino acid sequence A that has or comprises a certain % amino acid sequence identity to, with, or against a given amino acid sequence B) is calculated as follows:

100 times the fraction X/Y

where X is the number of amino acid residues scored as identical matches by the sequence alignment program ALIGN-2 in that program's alignment of A and B, and where Y is the total number of amino acid residues in B. It will be appreciated that where the length of amino acid sequence A is not equal to the length of amino acid sequence B, the % amino acid sequence identity of A to B will not equal the % amino acid sequence identity of B to A. Unless specifically stated otherwise, all % amino acid sequence identity values used herein are obtained as described in the immediately preceding paragraph using the ALIGN-2 computer program.

The term “pharmaceutical formulation” refers to a preparation which is in such form as to permit the biological activity of an active ingredient contained therein to be effective, and which contains no additional components which are unacceptably toxic to a subject to which the formulation would be administered.

A “pharmaceutically acceptable carrier” refers to an ingredient in a pharmaceutical formulation, other than an active ingredient, which is nontoxic to a subject. A pharmaceutically acceptable carrier includes, but is not limited to, a buffer, excipient, stabilizer, or preservative.

As used herein, “treatment” (and grammatical variations thereof such as “treat” or “treating”) refers to clinical intervention in an attempt to alter the natural course of the individual being treated, and can be performed either for prophylaxis or during the course of clinical pathology. Desirable effects of treatment include, but are not limited to, preventing occurrence or recurrence of disease, alleviation of symptoms, diminishment of any direct or indirect pathological consequences of the disease, preventing metastasis, decreasing the rate of disease progression, amelioration or palliation of the disease state, and remission or improved prognosis. In some embodiments, antibodies of the invention are used to delay development of a disease or to slow the progression of a disease.

By “co-administering” is meant intravenously administering two (or more) drugs during the same administration, rather than sequential infusions of the two or more drugs. Generally, this will involve combining the two (or more) drugs into the same IV bag prior to co-administration thereof.

A drug that is administered “concurrently” with one or more other drugs is administered during the same treatment cycle, on the same day of treatment as the one or more other drugs, and, optionally, at the same time as the one or more other drugs. For instance, for cancer therapies given every 3 weeks, the concurrently administered drugs are each administered on day-1 of a 3-week cycle.

A “chemotherapy” is use of a chemotherapeutic agent useful in the treatment of cancer.

A “chemotherapeutic agent” is a chemical compound useful in the treatment of cancer, regardless of mechanism of action. Classes of chemotherapeutic agents include, but are not limited to: alkylating agents, antimetabolites, spindle poison plant alkaloids, cytotoxic/antitumor antibiotics, topoisomerase inhibitors, antibodies, photosensitizers, and kinase inhibitors. Examples of chemotherapeutic agents include: anthracyclines, such as epirubicin or doxorubicin (ADRIAMYCIN®), cyclophosphamide (CYTOXAN®, NEOSAR®), anthracycline and cyclophosphamide in combination (“AC”); a taxane, e.g., docetaxel (TAXOTERE®) or paclitaxel (TAXOL®), 5-FU (fluorouracil, 5-fluorouracil, CAS No. 51-21-8), lapatinib (TYKERB®), capecitabine (XELODA®), gemcitabine (GEMZAR®, Lilly), PD-0325901 (CAS No. 391210-10-9, Pfizer), cisplatin (cis-diamine,dichloroplatinum(II), CAS No. 15663-27-1), carboplatin (CAS No. 41575-94-4), temozolomide (4-methyl-5-oxo-2,3,4,6,8-pentazabicyclo[4.3.0]nona-2,7,9-triene-9-carboxamide, CAS No. 85622-93-1, TEMODAR®, TEMODAL®, Schering Plough), tamoxifen ((Z)-2-[4-(1,2-diphenylbut-1-enyl)phenoxy]-N,N-dimethyl-ethanamine, NOLVADEX®, ISTUBAL®, VALODEX®).

More examples of chemotherapeutic agents include: oxaliplatin (ELOXATIN®, Sanofi), bortezomib (VELCADE®, Millennium Pharm.), sutent (SUNITINIB®, SU11248, Pfizer), letrozole (FEMARA®, Novartis), imatinib mesylate (GLEEVEC®, Novartis), XL-518 (MEK inhibitor, Exelixis, WO 2007/044515), ARRY-886 (Mek inhibitor, AZD6244, Array BioPharma, Astra Zeneca), SF-1126 (PI3K inhibitor, Semafore Pharmaceuticals), BEZ-235 (PI3K inhibitor, Novartis), XL-147 (PI3K inhibitor, Exelixis), PTK787/ZK 222584 (Novartis), fulvestrant (FASLODEX®, AstraZeneca), leucovorin (folinic acid), rapamycin (sirolimus, RAPAMUNE®, Wyeth), lonafarnib (SARASAR™, SCH 66336, Schering Plough), sorafenib (NEXAVAR®, BAY43-9006, Bayer Labs), gefitinib (IRESSA®, AstraZeneca), irinotecan (CAMPTOSAR®, CPT-11, Pfizer), tipifarnib (ZARNESTRA™, Johnson & Johnson), ABRAXANE™ (Cremophor-free), albumin-engineered nanoparticle formulations of paclitaxel (American Pharmaceutical Partners, Schaumberg, II), vandetanib (rINN, ZD6474, ZACTIMA®, AstraZeneca), chloranmbucil, AG1478, AG1571 (SU 5271; Sugen), temsirolimus (TORISEL®, Wyeth), pazopanib (GlaxoSmithKline), canfosfamide (TELCYTA®, Telik), thiotepa and cyclosphosphamide (CYTOXAN®, NEOSAR®); alkyl sulfonates such as busulfan, improsulfan and piposulfan; aziridines such as benzodopa, carboquone, meturedopa, and uredopa; ethylenimines and methylamelamines including altretamine, triethylenemelamine, triethylenephosphoramide, triethylenethiophosphoramide and trimethylomelamine; acetogenins (especially bullatacin and bullatacinone); a camptothecin (including the synthetic analog topotecan); bryostatin; callystatin; CC-1065 (including its adozelesin, carzelesin and bizelesin synthetic analogs); cryptophycins (particularly cryptophycin 1 and cryptophycin 8); dolastatin; duocarmycin (including the synthetic analogs, KW-2189 and CB1-TM1); eleutherobin; pancratistatin; a sarcodictyin; spongistatin; nitrogen mustards such as chlorambucil, chlornaphazine, chlorophosphamide, estramustine, ifosfamide, mechlorethamine, mechlorethamine oxide hydrochloride, melphalan, novembichin, phenesterine, prednimustine, trofosfamide, uracil mustard; nitrosoureas such as carmustine, chlorozotocin, fotemustine, lomustine, nimustine, and ranimnustine; antibiotics such as the enediyne antibiotics (e.g., calicheamicin, calicheamicin gammall, calicheamicin omegaI1 (Angew Chem. Intl. Ed. Engl. (1994) 33:183-186); dynemicin, dynemicin A; bisphosphonates, such as clodronate; an esperamicin; as well as neocarzinostatin chromophore and related chromoprotein enediyne antibiotic chromophores), aclacinomysins, actinomycin, authramycin, azaserine, bleomycins, cactinomycin, carabicin, carminomycin, carzinophilin, chromomycinis, dactinomycin, daunorubicin, detorubicin, 6-diazo-5-oxo-L-norleucine, morpholino-doxorubicin, cyanomorpholino-doxorubicin, 2-pyrrolino-doxorubicin and deoxydoxorubicin), epirubicin, esorubicin, idarubicin, marcellomycin, mitomycins such as mitomycin C, mycophenolic acid, nogalamycin, olivomycins, peplomycin, porfiromycin, puromycin, quelamycin, rodorubicin, streptonigrin, streptozocin, tubercidin, ubenimex, zinostatin, zorubicin; anti-metabolites such as methotrexate and 5-fluorouracil (5-FU); folic acid analogs such as denopterin, methotrexate, pteropterin, trimetrexate; purine analogs such as fludarabine, 6-mercaptopurine, thiamiprine, thioguanine; pyrimidine analogs such as ancitabine, azacitidine, 6-azauridine, carmofur, cytarabine, dideoxyuridine, doxifluridine, enocitabine, floxuridine; androgens such as calusterone, dromostanolone propionate, epitiostanol, mepitiostane, testolactone; anti-adrenals such as aminoglutethimide, mitotane, trilostane; folic acid replenisher such as frolinic acid; aceglatone; aldophosphamide glycoside; aminolevulinic acid; eniluracil; amsacrine; bestrabucil; bisantrene; edatraxate; defofamine; demecolcine; diaziquone; elfornithine; elliptinium acetate; an epothilone; etoglucid; gallium nitrate; hydroxyurea; lentinan; lonidainine; maytansinoids such as maytansine and ansamitocins; mitoguazone; mitoxantrone; mopidanmol; nitraerine; pentostatin; phenamet; pirarubicin; losoxantrone; podophyllinic acid; 2-ethylhydrazide; procarbazine; PSK® polysaccharide complex (JHS Natural Products, Eugene, Oreg.); razoxane; rhizoxin; sizofiran; spirogermanium; tenuazonic acid; triaziquone; 2,2′,2″-trichlorotriethylamine; trichothecenes (T-2 toxin, verracurin A, roridin A and anguidine); urethan; vindesine; dacarbazine; mannomustine; mitobronitol; mitolactol; pipobroman; gacytosine; arabinoside (Ara-C); cyclophosphamide; thiotepa; 6-thioguanine; mercaptopurine; methotrexate; platinum analogs such as cisplatin and carboplatin; vinblastine; etoposide (VP-16); ifosfamide; mitoxantrone; vincristine; vinorelbine (NAVELBINE®); novantrone; teniposide; edatrexate; daunomycin; aminopterin; ibandronate; CPT-11; topoisomerase inhibitor RFS 2000; difluoromethylornithine (DMFO); retinoids such as retinoic acid; and pharmaceutically acceptable salts, acids and derivatives of any of the above.

A “fixed” or “flat” dose of a therapeutic agent herein refers to a dose that is administered to a human patient without regard for the weight (WT) or body surface area (BSA) of the patient. The fixed or flat dose is therefore not provided as a mg/kg dose or a mg/m2 dose, but rather as an absolute amount of the therapeutic agent.

A “loading” dose herein generally comprises an initial dose of a therapeutic agent administered to a patient, and is followed by one or more maintenance dose(s) thereof. Generally, a single loading dose is administered, but multiple loading doses are contemplated herein. Usually, the amount of loading dose(s) administered exceeds the amount of the maintenance dose(s) administered and/or the loading dose(s) are administered more frequently than the maintenance dose(s), so as to achieve the desired steady-state concentration of the therapeutic agent earlier than can be achieved with the maintenance dose(s).

A “maintenance” dose herein refers to one or more doses of a therapeutic agent administered to the patient over a treatment period. Usually, the maintenance doses are administered at spaced treatment intervals, such as approximately every week, approximately every 2 weeks, approximately every 3 weeks, or approximately every 4 weeks, preferably every 3 weeks.

“Infusion” or “infusing” refers to the introduction of a drug-containing solution into the body through a vein for therapeutic purposes. Generally, this is achieved via an intravenous (IV) bag.

An “intravenous bag” or “IV bag” is a bag that can hold a solution which can be administered via the vein of a patient. In one embodiment, the solution is a saline solution (e.g. about 0.9% or about 0.45% NaCl). Optionally, the IV bag is formed from polyolefin or polyvinal chloride.

The term “variable region” or “variable domain” refers to the domain of an antibody heavy or light chain that is involved in binding the antibody to antigen. The variable domains of the heavy chain and light chain (VH and VL, respectively) of a native antibody generally have similar structures, with each domain comprising four conserved framework regions (FRs) and three hypervariable regions (HVRs). (See, e.g., Kindt et al. Kuby Immunology, 6^(th) ed., W.H. Freeman and Co., page 91 (2007).) A single VH or VL domain may be sufficient to confer antigen-binding specificity. Furthermore, antibodies that bind a particular antigen may be isolated using a VH or VL domain from an antibody that binds the antigen to screen a library of complementary VL or VH domains, respectively. See, e.g., Portolano et al., J. Immunol. 150:880-887 (1993); Clarkson et al., Nature 352:624-628 (1991).

The term “vector,” as used herein, refers to a nucleic acid molecule capable of propagating another nucleic acid to which it is linked. The term includes the vector as a self-replicating nucleic acid structure as well as the vector incorporated into the genome of a host cell into which it has been introduced. Certain vectors are capable of directing the expression of nucleic acids to which they are operatively linked. Such vectors are referred to herein as “expression vectors.”

“Alkyl” is C₁-C₁₈ hydrocarbon containing normal, secondary, tertiary or cyclic carbon atoms. Examples are methyl (Me, —CH₃), ethyl (Et, —CH₂CH₃), 1-propyl (n-Pr, n-propyl, —CH₂CH₂CH₃), 2-propyl (i-Pr, i-propyl, —CH(CH₃)₂), 1-butyl (n-Bu, n-butyl, —CH₂CH₂CH₂CH₃), 2-methyl-1-propyl (i-Bu, i-butyl, —CH₂CH(CH₃)₂), 2-butyl (s-Bu, s-butyl, —CH(CH₃)CH₂CH₃), 2-methyl-2-propyl t-butyl, —C(CH₃)₃), 1-pentyl (n-pentyl, —CH₂CH₂CH₂CH₂CH₃), 2-pentyl (—CH(CH₃)CH₂CH₂CH₃), 3-pentyl (—CH(CH₂CH₃)₂), 2-methyl-2-butyl (—C(CH₃)₂CH₂CH₃), 3-methyl-2-butyl (—CH(CH₃)CH(CH₃)₂), 3-methyl-1-butyl (—CH₂CH₂CH(CH₃)₂), 2-methyl-1-butyl (—CH₂CH(CH₃)CH₂CH₃), 1-hexyl (—CH₂CH₂CH₂CH₂CH₂CH₃), 2-hexyl (—CH(CH₃)CH₂CH₂CH₂CH₃), 3-hexyl (—CH(CH₂CH₃)(CH₂CH₂CH₃)), 2-methyl-2-pentyl (—C(CH₃)₂CH₂CH₂CH₃), 3-methyl-2-pentyl (—CH(CH₃)CH(CH₃)CH₂CH₃), 4-methyl-2-pentyl (—CH(CH₃)CH₂CH(CH₃)₂), 3-methyl-3-pentyl (—C(CH₃)(CH₂CH₃)₂), 2-methyl-3-pentyl (—CH(CH₂CH₃)CH(CH₃)₂), 2,3-dimethyl-2-butyl (—C(CH₃)₂CH(CH₃)₂), 3,3-dimethyl-2-butyl (—CH(CH₃)C(CH₃)₃.

The term “C₁-C₈ alkyl,” as used herein refers to a straight chain or branched, saturated or unsaturated hydrocarbon having from 1 to 8 carbon atoms. Representative “C₁-C₈ alkyl” groups include, but are not limited to, -methyl, -ethyl, -n-propyl, -n-butyl, -n-pentyl, -n-hexyl, -n-heptyl, -n-octyl, -n-nonyl and -n-decyl; while branched C₁-C₈ alkyls include, but are not limited to, -isopropyl, -sec-butyl, -isobutyl, -tert-butyl, -isopentyl, 2-methylbutyl, unsaturated C₁-C₈ alkyls include, but are not limited to, -vinyl, -allyl, -1-butenyl, -2-butenyl, -isobutylenyl, -1-pentenyl, -2-pentenyl, -3-methyl-1-butenyl, -2-methyl-2-butenyl, -2,3-dimethyl-2-butenyl, 1-hexyl, 2-hexyl, 3-hexyl,-acetylenyl, -propynyl, -1-butynyl, -2-butynyl, -1-pentynyl, -2-pentynyl, -3-methyl-1 butynyl. A C₁-C₈ alkyl group can be unsubstituted or substituted with one or more groups including, but not limited to, —C₁-C₈ alkyl, —O—(C₁-C₈ alkyl), -aryl, —C(O)R′, —OC(O)R′, —C(O)OR′, —C(O)NH₂, —C(O)NHR′, —C(O)N(R′)₂—NHC(O)R′, —SO₃R′, —S(O)₂R′, —S(O)R′, —OH, -halogen, —N₃, —NH₂, —NH(R′), —N(R′)₂ and —CN; where each R′ is independently selected from H, —C₁-C₈ alkyl and aryl.

The term “C₁-C₁₂ alkyl,” as used herein refers to a straight chain or branched, saturated or unsaturated hydrocarbon having from 1 to 12 carbon atoms. A C₁-C₁₂ alkyl group can be unsubstituted or substituted with one or more groups including, but not limited to, —C₁-C₈ alkyl, —O—(C₁-C₈ alkyl), -aryl, —C(O)R′, —OC(O)R′, —C(O)OR′, —C(O)NH₂, —C(O)NHR′, —C(O)N(R′)₂—NHC(O)R′, —SO₃R′, —S(O)₂R′, —S(O)R′, —OH, -halogen, —N₃, —NH₂, —NH(R′), —N(R′)₂ and —CN; where each R′ is independently selected from H, —C₁-C₈ alkyl and aryl.

The term “C₁-C₆ alkyl,” as used herein refers to a straight chain or branched, saturated or unsaturated hydrocarbon having from 1 to 6 carbon atoms. Representative “C₁-C₆ alkyl” groups include, but are not limited to, -methyl, -ethyl, -n-propyl, -n-butyl, -n-pentyl, -and n-hexyl; while branched C₁-C₆ alkyls include, but are not limited to, -isopropyl, -sec-butyl, -isobutyl, -tert-butyl, -isopentyl, and 2-methylbutyl; unsaturated C₁-C₆ alkyls include, but are not limited to, -vinyl, -allyl, -1-butenyl, -2-butenyl, and -isobutylenyl, -1-pentenyl, -2-pentenyl, -3-methyl-1-butenyl, -2-methyl-2-butenyl, -2,3-dimethyl-2-butenyl, 1-hexyl, 2-hexyl, and 3-hexyl. A C₁-C₆ alkyl group can be unsubstituted or substituted with one or more groups, as described above for C₁-C₈ alkyl group.

The term “C₁-C₄ alkyl,” as used herein refers to a straight chain or branched, saturated or unsaturated hydrocarbon having from 1 to 4 carbon atoms. Representative “C₁-C₄ alkyl” groups include, but are not limited to, -methyl, -ethyl, -n-propyl, -n-butyl; while branched C₁-C₄ alkyls include, but are not limited to, -isopropyl, -sec-butyl, -isobutyl, -tert-butyl; unsaturated C₁-C₄ alkyls include, but are not limited to, -vinyl, -allyl, -1-butenyl, -2-butenyl, and -isobutylenyl. A C₁-C₄ alkyl group can be unsubstituted or substituted with one or more groups, as described above for C₁-C₈ alkyl group.

“Alkoxy” is an alkyl group singly bonded to an oxygen. Exemplary alkoxy groups include, but are not limited to, methoxy (—OCH₃) and ethoxy (—OCH₂CH₃). A “C₁-C₅ alkoxy” is an alkoxy group with 1 to 5 carbon atoms. Alkoxy groups may can be unsubstituted or substituted with one or more groups, as described above for alkyl groups.

“Alkenyl” is C₂-C₁₈ hydrocarbon containing normal, secondary, tertiary or cyclic carbon atoms with at least one site of unsaturation, i.e. a carbon-carbon, sp² double bond. Examples include, but are not limited to: ethylene or vinyl (—CH═CH₂), allyl (—CH₂CH═CH₂), cyclopentenyl (—C₅H₇), and 5-hexenyl (—CH₂ CH₂CH₂CH₂CH═CH₂). A “C₂-C₈ alkenyl” is a hydrocarbon containing 2 to 8 normal, secondary, tertiary or cyclic carbon atoms with at least one site of unsaturation, i.e. a carbon-carbon, sp² double bond.

“Alkynyl” is C₂-C₁₈ hydrocarbon containing normal, secondary, tertiary or cyclic carbon atoms with at least one site of unsaturation, i.e. a carbon-carbon, sp triple bond. Examples include, but are not limited to: acetylenic (—C≡CH) and propargyl (—CH₂C≡CH). A “C₂-C₈ alkynyl” is a hydrocarbon containing 2 to 8 normal, secondary, tertiary or cyclic carbon atoms with at least one site of unsaturation, i.e. a carbon-carbon, sp triple bond.

“Alkylene” refers to a saturated, branched or straight chain or cyclic hydrocarbon radical of 1-18 carbon atoms, and having two monovalent radical centers derived by the removal of two hydrogen atoms from the same or two different carbon atoms of a parent alkane. Typical alkylene radicals include, but are not limited to: methylene (—CH₂—) 1,2-ethyl (—CH₂CH₂—), 1,3-propyl (—CH₂CH₂CH₂—), 1,4-butyl (—CH₂CH₂CH₂CH₂—), and the like.

“Alkenylene” refers to an unsaturated, branched or straight chain or cyclic hydrocarbon radical of 2-18 carbon atoms, and having two monovalent radical centers derived by the removal of two hydrogen atoms from the same or two different carbon atoms of a parent alkene. Typical alkenylene radicals include, but are not limited to: 1,2-ethylene (—CH═CH—).

“Alkynylene” refers to an unsaturated, branched or straight chain or cyclic hydrocarbon radical of 2-18 carbon atoms, and having two monovalent radical centers derived by the removal of two hydrogen atoms from the same or two different carbon atoms of a parent alkyne. Typical alkynylene radicals include, but are not limited to: acetylene (—C≡C—), propargyl (—CH₂C≡C—), and 4-pentynyl (—CH₂CH₂CH₂C≡C—).

“Aryl” refers to a carbocyclic aromatic group. Examples of aryl groups include, but are not limited to, phenyl, naphthyl and anthracenyl. A carbocyclic aromatic group or a heterocyclic aromatic group can be unsubstituted or substituted with one or more groups including, but not limited to, —C₁-C₈ alkyl, —O—(C₁-C₈ alkyl), -aryl, —C(O)R′, —OC(O)R′, —C(O)OR′, —C(O)NH₂, —C(O)NHR′, —C(O)N(R′)₂—NHC(O)R′, —S(O)₂R′, —S(O)R′, —OH, -halogen, —N₃, —NH₂, —NH(R′), —N(R′)₂ and —CN; wherein each R′ is independently selected from H, —C₁-C₈ alkyl and aryl.

A “C₅-C₂₀ aryl” is an aryl group with 5 to 20 carbon atoms in the carbocyclic aromatic rings. Examples of C₅-C₂₀ aryl groups include, but are not limited to, phenyl, naphthyl and anthracenyl. A C₅-C₂₀ aryl group can be substituted or unsubstituted as described above for aryl groups. A “C₅-C₁₄ aryl” is an aryl group with 5 to 14 carbon atoms in the carbocyclic aromatic rings. Examples of C₅-C₁₄ aryl groups include, but are not limited to, phenyl, naphthyl and anthracenyl. A C₅-C₁₄ aryl group can be substituted or unsubstituted as described above for aryl groups.

An “arylene” is an aryl group which has two covalent bonds and can be in the ortho, meta, or para configurations as shown in the following structures:

in which the phenyl group can be unsubstituted or substituted with up to four groups including, but not limited to, —C₁-C₈ alkyl, —O—(C₁-C₈ alkyl), -aryl, —C(O)R′, —OC(O)R′, —C(O)OR′, —C(O)NH₂, —C(O)NHR′, —C(O)N(R′)₂—NHC(O)R′, —S(O)₂R′, —S(O)R′, —OH, -halogen, —N₃, —NH₂, —NH(R′), —N(R′)₂ and —CN; wherein each R′ is independently selected from H, —C₁-C₈ alkyl and aryl.

“Arylalkyl” refers to an acyclic alkyl radical in which one of the hydrogen atoms bonded to a carbon atom, typically a terminal or sp³ carbon atom, is replaced with an aryl radical. Typical arylalkyl groups include, but are not limited to, benzyl, 2-phenylethan-1-yl, 2-phenylethen-1-yl, naphthylmethyl, 2-naphthylethan-1-yl, 2-naphthylethen-1-yl, naphthobenzyl, 2-naphthophenylethan-1-yl and the like. The arylalkyl group comprises 6 to 20 carbon atoms, e.g. the alkyl moiety, including alkanyl, alkenyl or alkynyl groups, of the arylalkyl group is 1 to 6 carbon atoms and the aryl moiety is 5 to 14 carbon atoms.

“Heteroarylalkyl” refers to an acyclic alkyl radical in which one of the hydrogen atoms bonded to a carbon atom, typically a terminal or sp³ carbon atom, is replaced with a heteroaryl radical. Typical heteroarylalkyl groups include, but are not limited to, 2-benzimidazolylmethyl, 2-furylethyl, and the like. The heteroarylalkyl group comprises 6 to 20 carbon atoms, e.g. the alkyl moiety, including alkanyl, alkenyl or alkynyl groups, of the heteroarylalkyl group is 1 to 6 carbon atoms and the heteroaryl moiety is 5 to 14 carbon atoms and 1 to 3 heteroatoms selected from N, O, P, and S. The heteroaryl moiety of the heteroarylalkyl group may be a monocycle having 3 to 7 ring members (2 to 6 carbon atoms or a bicycle having 7 to 10 ring members (4 to 9 carbon atoms and 1 to 3 heteroatoms selected from N, O, P, and S), for example: a bicyclo[4,5], [5,5], [5,6], or [6,6]system.

“Substituted alkyl,” “substituted aryl,” and “substituted arylalkyl” mean alkyl, aryl, and arylalkyl respectively, in which one or more hydrogen atoms are each independently replaced with a substituent. Typical substituents include, but are not limited to, —X, —R, —O⁻, —OR, —SR, —S⁻, —NR₂, —NR₃, ═NR, —CX₃, —CN, —OCN, —SCN, —N═C═O, —NCS, —NO, —NO₂, ═N2, —N₃, NC(═O)R, —C(═O)R, —C(═O)NR₂, —SO₃ ⁻, —SO₃H, —S(═O)₂R, —OS(═O)₂OR, —S(═O)₂NR, —S(═O)R, —OP(═O)(OR)₂, —P(═O)(OR)₂, —PO₃, —PO₃H₂, —C(═O)R, —C(═O)X, —C(═S)R, —CO₂R, —CO₂, —C(═S)OR, —C(═O)SR, —C(═S)SR, —C(═O)NR₂, —C(═S)NR₂, —C(═NR)NR₂, where each X is independently a halogen: F, Cl, Br, or I; and each R is independently —H, C₂-C₁₈ alkyl, C₆-C₂₀ aryl, C₃-C₁₄ heterocycle, protecting group or prodrug moiety. Alkylene, alkenylene, and alkynylene groups as described above may also be similarly substituted.

“Heteroaryl” and “heterocycle” refer to a ring system in which one or more ring atoms is a heteroatom, e.g. nitrogen, oxygen, and sulfur. The heterocycle radical comprises 3 to 20 carbon atoms and 1 to 3 heteroatoms selected from N, O, P, and S. A heterocycle may be a monocycle having 3 to 7 ring members (2 to 6 carbon atoms and 1 to 3 heteroatoms selected from N, O, P, and S) or a bicycle having 7 to 10 ring members (4 to 9 carbon atoms and 1 to 3 heteroatoms selected from N, O, P, and S), for example: a bicyclo[4,5], [5,5], [5,6], or [6,6]system.

Exemplary heterocycles are described, e.g., in Paquette, Leo A., “Principles of Modern Heterocyclic Chemistry” (W.A. Benjamin, New York, 1968), particularly Chapters 1, 3, 4, 6, 7, and 9; “The Chemistry of Heterocyclic Compounds, A series of Monographs” (John Wiley & Sons, New York, 1950 to present), in particular Volumes 13, 14, 16, 19, and 28; and J. Am. Chem. Soc. (1960) 82:5566.

Examples of heterocycles include by way of example and not limitation pyridyl, dihydroypyridyl, tetrahydropyridyl(piperidyl), thiazolyl, tetrahydrothiophenyl, sulfur oxidized tetrahydrothiophenyl, pyrimidinyl, furanyl, thienyl, pyrrolyl, pyrazolyl, imidazolyl, tetrazolyl, benzofuranyl, thianaphthalenyl, indolyl, indolenyl, quinolinyl, isoquinolinyl, benzimidazolyl, piperidinyl, 4-piperidonyl, pyrrolidinyl, 2-pyrrolidonyl, pyrrolinyl, tetrahydrofuranyl, bis-tetrahydrofuranyl, tetrahydropyranyl, bis-tetrahydropyranyl, tetrahydroquinolinyl, tetrahydroisoquinolinyl, decahydroquinolinyl, octahydroisoquinolinyl, azocinyl, triazinyl, 6H-1,2,5-thiadiazinyl, 2H,6H-1,5,2-dithiazinyl, thienyl, thianthrenyl, pyranyl, isobenzofuranyl, chromenyl, xanthenyl, phenoxathinyl, 2H-pyrrolyl, isothiazolyl, isoxazolyl, pyrazinyl, pyridazinyl, indolizinyl, isoindolyl, 3H-indolyl, 1H-indazolyl, purinyl, 4H-quinolizinyl, phthalazinyl, naphthyridinyl, quinoxalinyl, quinazolinyl, cinnolinyl, pteridinyl, 4aH-carbazolyl, carbazolyl, β-carbolinyl, phenanthridinyl, acridinyl, pyrimidinyl, phenanthrolinyl, phenazinyl, phenothiazinyl, furazanyl, phenoxazinyl, isochromanyl, chromanyl, imidazolidinyl, imidazolinyl, pyrazolidinyl, pyrazolinyl, piperazinyl, indolinyl, isoindolinyl, quinuclidinyl, morpholinyl, oxazolidinyl, benzotriazolyl, benzisoxazolyl, oxindolyl, benzoxazolinyl, and isatinoyl.

By way of example and not limitation, carbon bonded heterocycles are bonded at position 2, 3, 4, 5, or 6 of a pyridine, position 3, 4, 5, or 6 of a pyridazine, position 2, 4, 5, or 6 of a pyrimidine, position 2, 3, 5, or 6 of a pyrazine, position 2, 3, 4, or 5 of a furan, tetrahydrofuran, thiofuran, thiophene, pyrrole or tetrahydropyrrole, position 2, 4, or 5 of an oxazole, imidazole or thiazole, position 3, 4, or 5 of an isoxazole, pyrazole, or isothiazole, position 2 or 3 of an aziridine, position 2, 3, or 4 of an azetidine, position 2, 3, 4, 5, 6, 7, or 8 of a quinoline or position 1, 3, 4, 5, 6, 7, or 8 of an isoquinoline. Still more typically, carbon bonded heterocycles include 2-pyridyl, 3-pyridyl, 4-pyridyl, 5-pyridyl, 6-pyridyl, 3-pyridazinyl, 4-pyridazinyl, 5-pyridazinyl, 6-pyridazinyl, 2-pyrimidinyl, 4-pyrimidinyl, 5-pyrimidinyl, 6-pyrimidinyl, 2-pyrazinyl, 3-pyrazinyl, 5-pyrazinyl, 6-pyrazinyl, 2-thiazolyl, 4-thiazolyl, or 5-thiazolyl.

By way of example and not limitation, nitrogen bonded heterocycles are bonded at position 1 of an aziridine, azetidine, pyrrole, pyrrolidine, 2-pyrroline, 3-pyrroline, imidazole, imidazolidine, 2-imidazoline, 3-imidazoline, pyrazole, pyrazoline, 2-pyrazoline, 3-pyrazoline, piperidine, piperazine, indole, indoline, 1H-indazole, position 2 of a isoindole, or isoindoline, position 4 of a morpholine, and position 9 of a carbazole, or β-carboline. Still more typically, nitrogen bonded heterocycles include 1-aziridyl, 1-azetedyl, 1-pyrrolyl, 1-imidazolyl, 1-pyrazolyl, and 1-piperidinyl.

A “C₃-C₈ heterocycle” refers to an aromatic or non-aromatic C₃-C₈ carbocycle in which one to four of the ring carbon atoms are independently replaced with a heteroatom from the group consisting of O, S and N. Representative examples of a C₃-C₈ heterocycle include, but are not limited to, benzofuranyl, benzothiophene, indolyl, benzopyrazolyl, coumarinyl, isoquinolinyl, pyrrolyl, thiophenyl, furanyl, thiazolyl, imidazolyl, pyrazolyl, triazolyl, quinolinyl, pyrimidinyl, pyridinyl, pyridonyl, pyrazinyl, pyridazinyl, isothiazolyl, isoxazolyl and tetrazolyl. A C₃-C₈ heterocycle can be unsubstituted or substituted with up to seven groups including, but not limited to, —C₁-C₈ alkyl, —O—(C₁-C₈ alkyl), -aryl, —C(O)R′, —OC(O)R′, —C(O)OR′, —C(O)NH₂, —C(O)NHR′, —C(O)N(R′)₂—NHC(O)R′, —S(O)₂R′, —S(O)R′, —OH, -halogen, —N₃, —NH₂, —NH(R′), —N(R′)₂ and —CN; wherein each R′ is independently selected from H, —C₁-C₈ alkyl and aryl.

“C₃-C₈ heterocyclo” refers to a C₃-C₈ heterocycle group defined above wherein one of the heterocycle group's hydrogen atoms is replaced with a bond. A C₃-C₈ heterocyclo can be unsubstituted or substituted with up to six groups including, but not limited to, —C₁-C₈ alkyl, —O—(C₁-C₈ alkyl), -aryl, —C(O)R′, —OC(O)R′, —C(O)OR′, —C(O)NH₂, —C(O)NHR′, —C(O)N(R′)₂—NHC(O)R′, —S(O)₂R′, —S(O)R′, —OH, -halogen, —N₃, —NH₂, —NH(R′), —N(R′)₂ and —CN; wherein each R′ is independently selected from H, —C₁-C₈ alkyl and aryl.

A “C₃-C₂₀ heterocycle” refers to an aromatic or non-aromatic C₃-C₈ carbocycle in which one to four of the ring carbon atoms are independently replaced with a heteroatom from the group consisting of O, S and N. A C₃-C₂₀ heterocycle can be unsubstituted or substituted with up to seven groups including, but not limited to, —C₁-C₈ alkyl, —O—(C₁-C₈ alkyl), -aryl, —C(O)R′, —OC(O)R′, —C(O)OR′, —C(O)NH₂, —C(O)NHR′, —C(O)N(R′)₂—NHC(O)R′, —S(O)₂R′, —S(O)R′, —OH, -halogen, —N₃, —NH₂, —NH(R′), —N(R′)₂ and —CN; wherein each R′ is independently selected from H, —C₁-C₈ alkyl and aryl.

“C₃-C₂₀ heterocyclo” refers to a C₃-C₂₀ heterocycle group defined above wherein one of the heterocycle group's hydrogen atoms is replaced with a bond.

“Carbocycle” means a saturated or unsaturated ring having 3 to 7 carbon atoms as a monocycle or 7 to 12 carbon atoms as a bicycle. Monocyclic carbocycles have 3 to 6 ring atoms, still more typically 5 or 6 ring atoms. Bicyclic carbocycles have 7 to 12 ring atoms, e.g. arranged as a bicyclo[4,5], [5,5], [5,6] or [6,6]system, or 9 or 10 ring atoms arranged as a bicyclo[5,6] or [6,6]system. Examples of monocyclic carbocycles include cyclopropyl, cyclobutyl, cyclopentyl, 1-cyclopent-1-enyl, 1-cyclopent-2-enyl, 1-cyclopent-3-enyl, cyclohexyl, 1-cyclohex-1-enyl, 1-cyclohex-2-enyl, 1-cyclohex-3-enyl, cycloheptyl, and cyclooctyl.

A “C₃-C₈ carbocycle” is a 3-, 4-, 5-, 6-, 7- or 8-membered saturated or unsaturated non-aromatic carbocyclic ring. Representative C₃-C₈ carbocycles include, but are not limited to, -cyclopropyl, -cyclobutyl, -cyclopentyl, -cyclopentadienyl, -cyclohexyl, -cyclohexenyl, -1,3-cyclohexadienyl, -1,4-cyclohexadienyl, -cycloheptyl, -1,3-cycloheptadienyl, -1,3,5-cycloheptatrienyl, -cyclooctyl, and -cyclooctadienyl. A C₃-C₈ carbocycle group can be unsubstituted or substituted with one or more groups including, but not limited to, —C₁-C₈ alkyl, —O—(C₁-C₈ alkyl), -aryl, —C(O)R′, —OC(O)R′, —C(O)OR′, —C(O)NH₂, —C(O)NHR′, —C(O)N(R′)₂—NHC(O)R′, —S(O)₂R′, —S(O)R′, —OH, -halogen, —N₃, —NH₂, —NH(R′), —N(R′)₂ and —CN; where each R′ is independently selected from H, —C₁-C₈ alkyl and aryl.

A “C₃-C₈ carbocyclo” refers to a C₃-C₈ carbocycle group defined above wherein one of the carbocycle groups' hydrogen atoms is replaced with a bond.

“Linker” refers to a chemical moiety comprising a covalent bond or a chain of atoms that covalently attaches an antibody to a drug moiety. In various embodiments, linkers include a divalent radical such as an alkyldiyl, an aryldiyl, a heteroaryldiyl, moieties such as: —(CR₂)_(n)O(CR₂)_(n)—, repeating units of alkyloxy (e.g. polyethylenoxy, PEG, polymethyleneoxy) and alkylamino (e.g. polyethyleneamino, Jeffamine™); and diacid ester and amides including succinate, succinamide, diglycolate, malonate, and caproamide. In various embodiments, linkers can comprise one or more amino acid residues, such as valine, phenylalanine, lysine, and homolysine.

The term “chiral” refers to molecules which have the property of non-superimposability of the mirror image partner, while the term “achiral” refers to molecules which are superimposable on their mirror image partner.

The term “stereoisomers” refers to compounds which have identical chemical constitution, but differ with regard to the arrangement of the atoms or groups in space.

“Diastereomer” refers to a stereoisomer with two or more centers of chirality and whose molecules are not mirror images of one another. Diastereomers have different physical properties, e.g. melting points, boiling points, spectral properties, and reactivities. Mixtures of diastereomers may separate under high resolution analytical procedures such as electrophoresis and chromatography.

“Enantiomers” refer to two stereoisomers of a compound which are non-superimposable mirror images of one another.

Stereochemical definitions and conventions used herein generally follow S. P. Parker, Ed., McGraw-Hill Dictionary of Chemical Terms (1984) McGraw-Hill Book Company, New York; and Eliel, E. and Wilen, S., Stereochemistry of Organic Compounds (1994) John Wiley & Sons, Inc., New York. Many organic compounds exist in optically active forms, i.e., they have the ability to rotate the plane of plane-polarized light. In describing an optically active compound, the prefixes D and L, or R and S, are used to denote the absolute configuration of the molecule about its chiral center(s). The prefixes d and 1 or (+) and (−) are employed to designate the sign of rotation of plane-polarized light by the compound, with (−) or 1 meaning that the compound is levorotatory. A compound prefixed with (+) or d is dextrorotatory. For a given chemical structure, these stereoisomers are identical except that they are mirror images of one another. A specific stereoisomer may also be referred to as an enantiomer, and a mixture of such isomers is often called an enantiomeric mixture. A 50:50 mixture of enantiomers is referred to as a racemic mixture or a racemate, which may occur where there has been no stereoselection or stereospecificity in a chemical reaction or process. The terms “racemic mixture” and “racemate” refer to an equimolar mixture of two enantiomeric species, devoid of optical activity.

“Leaving group” refers to a functional group that can be substituted by another functional group. Certain leaving groups are well known in the art, and examples include, but are not limited to, a halide (e.g., chloride, bromide, iodide), methanesulfonyl(mesyl), p-toluenesulfonyl(tosyl), trifluoromethylsulfonyl(triflate), and trifluoromethylsulfonate.

The term “protecting group” refers to a substituent that is commonly employed to block or protect a particular functionality while reacting other functional groups on the compound. For example, an “amino-protecting group” is a substituent attached to an amino group that blocks or protects the amino functionality in the compound. Suitable amino-protecting groups include, but are not limited to, acetyl, trifluoroacetyl, t-butoxycarbonyl (BOC), benzyloxycarbonyl (CBZ) and 9-fluorenylmethylenoxycarbonyl (Fmoc). For a general description of protecting groups and their use, see T. W. Greene, Protective Groups in Organic Synthesis, John Wiley & Sons, New York, 1991, or a later edition.

II. Compositions and Methods

In one aspect, the invention is based, in part, on antibodies that bind to HER2 and immunoconjugates comprising such antibodies. Antibodies and immunoconjugates of the invention are useful, e.g., for the diagnosis or treatment of HER2-positive cancers.

A. Exemplary Anti-HER2 Antibodies

Provided herein are isolated antibodies that bind to domain I of HER2. In some embodiments, the antibodies do not interfere with trastuzumab and/or pertuzumab binding to HER2. In some embodiments, the antibodies do not interfere with trastuzumab binding to HER2 and do not interfere with pertuzumab binding to HER2. In any of the embodiments described herein, the antibodies may be monoclonal antibodies. In some embodiments, the antibodies may be human antibodies, humanized antibodies, or chimeric antibodies.

An exemplary naturally occurring human HER2 precursor protein sequence, with signal sequence (amino acids 1-22) is provided in SEQ ID NO: 1, and the corresponding mature HER2 protein sequence corresponds to amino acids 23-1255 of SEQ ID NO: 1. In some embodiments, domain I of HER2 has the amino acid sequence of SEQ ID NO: 35, domain II has the amino acid sequence of SEQ ID NO: 36, domain III has the amino acid sequence of SEQ ID NO: 37, and domain IV has the amino acid sequence of SEQ ID NO: 38 (see FIG. 10).

Antibody hu7C2 and Other Embodiments

In some embodiments, an anti-HER2 antibody is provided that comprises at least one, two, three, four, five, or six HVRs selected from (a) HVR—H1 comprising the amino acid sequence of SEQ ID NO: 15; (b) HVR—H2 comprising the amino acid sequence of SEQ ID NO: 16; (c) HVR—H3 comprising the amino acid sequence of SEQ ID NO: 17; (d) HVR-L1 comprising the amino acid sequence of SEQ ID NO: 12; (e) HVR-L2 comprising the amino acid sequence of SEQ ID NO: 13; and (f) HVR-L3 comprising the amino acid sequence of SEQ ID NO: 14. In some embodiments, an anti-HER2 antibody is provided that comprises an HVR—H2 comprising the amino acid sequence of SEQ ID NO: 16 and at least one, two, three, four, or five HVRs selected from (a) HVR—H1 comprising the amino acid sequence of SEQ ID NO: 15; (b) HVR—H3 comprising the amino acid sequence of SEQ ID NO: 17; (c) HVR-L1 comprising the amino acid sequence of SEQ ID NO: 12; (d) HVR-L2 comprising the amino acid sequence of SEQ ID NO: 13; and (e) HVR-L3 comprising the amino acid sequence of SEQ ID NO: 14.

In one aspect, an antibody is provided that comprises at least one, at least two, or all three VH HVR sequences selected from (a) HVR—H1 comprising the amino acid sequence of SEQ ID NO: 15; (b) HVR—H2 comprising the amino acid sequence of SEQ ID NO: 16; and (c) HVR—H3 comprising the amino acid sequence of SEQ ID NO: 17. In one embodiment, the antibody comprises HVR—H3 comprising the amino acid sequence of SEQ ID NO: 17. In one embodiment, the antibody comprises HVR—H2 comprising the amino acid sequence of SEQ ID NO: 16. In another embodiment, the antibody comprises HVR—H3 comprising the amino acid sequence of SEQ ID NO: 17 and HVR-L3 comprising the amino acid sequence of SEQ ID NO: 14. In a further embodiment, the antibody comprises HVR—H3 comprising the amino acid sequence of SEQ ID NO: 17, HVR-L3 comprising the amino acid sequence of SEQ ID NO: 14, and HVR—H2 comprising the amino acid sequence of SEQ ID NO: 16. In a further embodiment, the antibody comprises (a) HVR—H1 comprising the amino acid sequence of SEQ ID NO: 15; (b) HVR—H2 comprising the amino acid sequence of SEQ ID NO: 16; and (c) HVR—H3 comprising the amino acid sequence of SEQ ID NO: 17.

In another aspect, an antibody is provided that comprises at least one, at least two, or all three VL HVR sequences selected from (a) HVR-L1 comprising the amino acid sequence of SEQ ID NO: 12; (b) HVR-L2 comprising the amino acid sequence of SEQ ID NO: 13; and (c) HVR-L3 comprising the amino acid sequence of SEQ ID NO: 14. In one embodiment, the antibody comprises (a) HVR-L1 comprising the amino acid sequence of SEQ ID NO: 12; (b) HVR-L2 comprising the amino acid sequence of SEQ ID NO: 13; and (c) HVR-L3 comprising the amino acid sequence of SEQ ID NO: 14.

In another aspect, an antibody comprises (a) a VH domain comprising at least one, at least two, or all three VH HVR sequences selected from (i) HVR—H1 comprising the amino acid sequence of SEQ ID NO: 15, (ii) HVR—H2 comprising the amino acid sequence of SEQ ID NO: 16, and (iii) HVR—H3 comprising an amino acid sequence selected from SEQ ID NO: 17; and (b) a VL domain comprising at least one, at least two, or all three VL HVR sequences selected from (i) HVR-L1 comprising the amino acid sequence of SEQ ID NO: 12, (ii) HVR-L2 comprising the amino acid sequence of SEQ ID NO: 13, and (c) HVR-L3 comprising the amino acid sequence of SEQ ID NO: 14.

In another aspect, an antibody is provided that comprises (a) HVR—H1 comprising the amino acid sequence of SEQ ID NO: 15; (b) HVR—H2 comprising the amino acid sequence of SEQ ID NO: 16; (c) HVR—H3 comprising the amino acid sequence of SEQ ID NO: 17; (d) HVR-L1 comprising the amino acid sequence of SEQ ID NO: 12; (e) HVR-L2 comprising the amino acid sequence of SEQ ID NO: 13; and (f) HVR-L3 comprising the amino acid sequence of SEQ ID NO: 14.

In any of the above embodiments, an anti-HER2 antibody is humanized. In one embodiment, an anti-HER2 antibody comprises HVRs as in any of the above embodiments, and further comprises a human acceptor framework, e.g. a human immunoglobulin framework or a human consensus framework. In certain embodiments, the human acceptor framework is the human VL kappa IV consensus (VL_(KIV)) framework and/or the VH framework VH₁. In certain embodiments, the human acceptor framework is the human VL kappa IV consensus (VL_(KIV)) framework and/or the VH framework VH₁ comprising any one of the mutations described herein.

In another aspect, an anti-HER2 antibody comprises a heavy chain variable domain (VH) sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to the amino acid sequence of SEQ ID NO: 11. In certain embodiments, a VH sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% identity to the amino acid sequence of SEQ ID NO:11 contains substitutions (e.g., conservative substitutions), insertions, or deletions relative to the reference sequence, but an anti-HER2 antibody comprising that sequence retains the ability to bind to HER2. In certain embodiments, a total of 1 to 10 amino acids have been substituted, inserted and/or deleted in SEQ ID NO: 11. In certain embodiments, a total of 1 to 5 amino acids have been substituted, inserted and/or deleted in SEQ ID NO: 11. In certain embodiments, substitutions, insertions, or deletions occur in regions outside the HVRs (i.e., in the FRs). Optionally, the anti-HER2 antibody comprises the VH sequence of SEQ ID NO: 11, including post-translational modifications of that sequence. In a particular embodiment, the VH comprises one, two or three HVRs selected from: (a) HVR—H1 comprising the amino acid sequence of SEQ ID NO: 15, (b) HVR—H2 comprising the amino acid sequence of SEQ ID NO: 16, and (c) HVR—H3 comprising the amino acid sequence of SEQ ID NO: 17.

In another aspect, an anti-HER2 antibody is provided, wherein the antibody comprises a light chain variable domain (VL) having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to the amino acid sequence of SEQ ID NO: 10. In certain embodiments, a VL sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% identity to the amino acid sequence of SEQ ID NO:10 contains substitutions (e.g., conservative substitutions), insertions, or deletions relative to the reference sequence, but an anti-HER2 antibody comprising that sequence retains the ability to bind to HER2. In certain embodiments, a total of 1 to 10 amino acids have been substituted, inserted and/or deleted in SEQ ID NO: 10. In certain embodiments, a total of 1 to 5 amino acids have been substituted, inserted and/or deleted in SEQ ID NO: 10. In certain embodiments, the substitutions, insertions, or deletions occur in regions outside the HVRs (i.e., in the FRs). Optionally, the anti-HER2 antibody comprises the VL sequence of SEQ ID NO: 10, including post-translational modifications of that sequence. In a particular embodiment, the VL comprises one, two or three HVRs selected from (a) HVR-L1 comprising the amino acid sequence of SEQ ID NO: 12; (b) HVR-L2 comprising the amino acid sequence of SEQ ID NO: 13; and (c) HVR-L3 comprising the amino acid sequence of SEQ ID NO: 14.

In another aspect, an anti-HER2 antibody is provided, wherein the antibody comprises a VH as in any of the embodiments provided above, and a VL as in any of the embodiments provided above.

In one embodiment, the antibody comprises the VH and VL sequences in SEQ ID NO: 11 and SEQ ID NO: 10, respectively, including post-translational modifications of those sequences.

In a further aspect, provided are herein are antibodies that bind to the same epitope as an anti-HER2 antibody provided herein. For example, in certain embodiments, an antibody is provided that binds to the same epitope as an anti-HER2 antibody comprising a VH sequence of SEQ ID NO: 11 and a VL sequence of SEQ ID NO: 10, respectively.

In another aspect, an anti-HER2 antibody comprises a heavy chain sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to the amino acid sequence of SEQ ID NO: 19. In certain embodiments, a heavy chain sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% identity to the amino acid sequence of SEQ ID NO:19 contains substitutions (e.g., conservative substitutions), insertions, or deletions relative to the reference sequence, but an anti-HER2 antibody comprising that sequence retains the ability to bind to HER2. In certain embodiments, a total of 1 to 10 amino acids have been substituted, inserted and/or deleted in SEQ ID NO: 19. In certain embodiments, a total of 1 to 5 amino acids have been substituted, inserted and/or deleted in SEQ ID NO: 19. In certain embodiments, substitutions, insertions, or deletions occur in regions outside the HVRs (i.e., in the FRs). Optionally, the anti-HER2 antibody comprises the heavy chain sequence of SEQ ID NO: 19, including post-translational modifications of that sequence. In a particular embodiment, the heavy chain comprises one, two or three HVRs selected from: (a) HVR—H1 comprising the amino acid sequence of SEQ ID NO: 15, (b) HVR—H2 comprising the amino acid sequence of SEQ ID NO: 16, and (c) HVR—H3 comprising the amino acid sequence of SEQ ID NO: 17.

In another aspect, an anti-HER2 antibody is provided, wherein the antibody comprises a light chain having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to the amino acid sequence of SEQ ID NO: 18. In certain embodiments, a light chain sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% identity to the amino acid sequence of SEQ ID NO:18 contains substitutions (e.g., conservative substitutions), insertions, or deletions relative to the reference sequence, but an anti-HER2 antibody comprising that sequence retains the ability to bind to HER2. In certain embodiments, a total of 1 to 10 amino acids have been substituted, inserted and/or deleted in SEQ ID NO: 18. In certain embodiments, a total of 1 to 5 amino acids have been substituted, inserted and/or deleted in SEQ ID NO: 18. In certain embodiments, the substitutions, insertions, or deletions occur in regions outside the HVRs (i.e., in the FRs). Optionally, the anti-HER2 antibody comprises the light chain sequence of SEQ ID NO: 18, including post-translational modifications of that sequence. In a particular embodiment, the light chain comprises one, two or three HVRs selected from (a) HVR-L1 comprising the amino acid sequence of SEQ ID NO: 12; (b) HVR-L2 comprising the amino acid sequence of SEQ ID NO: 13; and (c) HVR-L3 comprising the amino acid sequence of SEQ ID NO: 14.

In another aspect, an anti-HER2 antibody is provided, wherein the antibody comprises a heavy chain as in any of the embodiments provided above, and a light chain as in any of the embodiments provided above.

In one embodiment, the antibody comprises the heavy chain and light chain sequences in SEQ ID NO: 19 and SEQ ID NO: 18, respectively, including post-translational modifications of those sequences.

In a further aspect, provided are herein are antibodies that bind to the same epitope as an anti-HER2 antibody provided herein. For example, in certain embodiments, an antibody is provided that binds to the same epitope as an anti-HER2 antibody comprising a heavy chain sequence of SEQ ID NO: 19 and a light chain sequence of SEQ ID NO: 18, respectively.

Provided herein are antibodies comprising a light chain variable domain comprising the HVR1-LC, HVR2-LC and HVR3-LC sequence according to Kabat numbering as depicted in FIG. 1 and a heavy chain variable domain comprising the HVR1-HC, HVR2-HC and HVR3-HC sequence according to Kabat numbering as depicted in FIG. 2. In some embodiments, the antibody comprises a light chain variable domain comprising the HVR1-LC, HVR2-LC and/or HVR3-LC sequence, and the FR1-LC, FR2-LC, FR3-LC and/or FR4-LC sequence as depicted in FIG. 1. In some embodiments, the antibody comprises a heavy chain variable domain comprising the HVR1-HC, HVR2-HC and/or HVR3-HC sequence, and the FR1-HC, FR2-HC, FR3-HC and/or FR4-HC sequence as depicted in FIG. 2.

In a further aspects, an anti-HER2 antibody according to any of the above embodiments is a monoclonal antibody, including a human antibody. In one embodiment, an anti-HER2 antibody is an antibody fragment, e.g., a Fv, Fab, Fab′, scFv, diabody, or F(ab′)₂ fragment. In another embodiment, the antibody is a substantially full length antibody, e.g., an IgG1 antibody, IgG2a antibody or other antibody class or isotype as defined herein.

In a further aspect, an anti-HER2 antibody according to any of the above embodiments may incorporate any of the features, singly or in combination, as described below.

1. Antibody Affinity

In certain embodiments, an antibody provided herein has a dissociation constant (Kd) of ≦1 μM, ≦100 nM, ≦50 nM, ≦10 nM, ≦5 nM, ≦1 nM, ≦0.1 nM, ≦0.01 nM, or ≦0.001 nM, and optionally is ≧10⁻¹³ M. (e.g. 10⁻⁸M or less, e.g. from 10⁻⁸M to 10⁻¹³M, e.g., from 10⁻⁹M to 10⁻¹³ M).

In one embodiment, Kd is measured by a radiolabeled antigen binding assay (RIA) performed with the Fab version of an antibody of interest and its antigen as described by the following assay. Solution binding affinity of Fabs for antigen is measured by equilibrating Fab with a minimal concentration of (¹²⁵I)-labeled antigen in the presence of a titration series of unlabeled antigen, then capturing bound antigen with an anti-Fab antibody-coated plate (see, e.g., Chen et al., J. Mol. Biol. 293:865-881(1999)). To establish conditions for the assay, MICROTITER® multi-well plates (Thermo Scientific) are coated overnight with 5 μg/ml of a capturing anti-Fab antibody (Cappel Labs) in 50 mM sodium carbonate (pH 9.6), and subsequently blocked with 2% (w/v) bovine serum albumin in PBS for two to five hours at room temperature (approximately 23° C.). In a non-adsorbent plate (Nunc #269620), 100 pM or 26 pM [¹²⁵I]-antigen are mixed with serial dilutions of a Fab of interest (e.g., consistent with assessment of the anti-VEGF antibody, Fab-12, in Presta et al., Cancer Res. 57:4593-4599 (1997)). The Fab of interest is then incubated overnight; however, the incubation may continue for a longer period (e.g., about 65 hours) to ensure that equilibrium is reached. Thereafter, the mixtures are transferred to the capture plate for incubation at room temperature (e.g., for one hour). The solution is then removed and the plate washed eight times with 0.1% polysorbate 20 (TWEEN-20®) in PBS. When the plates have dried, 150 μl/well of scintillant (MICROSCINT-20™; Packard) is added, and the plates are counted on a TOPCOUNT™ gamma counter (Packard) for ten minutes. Concentrations of each Fab that give less than or equal to 20% of maximal binding are chosen for use in competitive binding assays.

According to another embodiment, Kd is measured using surface plasmon resonance assays using a BIACORE®-2000 or a BIACORE®-3000 (BIAcore, Inc., Piscataway, N.J.) at 25° C. with immobilized antigen CMS chips at ˜10 response units (RU). Briefly, carboxymethylated dextran biosensor chips (CMS, BIACORE, Inc.) are activated with N-ethyl-N′-(3-dimethylaminopropyl)-carbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) according to the supplier's instructions. Antigen is diluted with 10 mM sodium acetate, pH 4.8, to 5 μg/ml (˜0.2 μM) before injection at a flow rate of 5 μl/minute to achieve approximately 10 response units (RU) of coupled protein. Following the injection of antigen, 1 M ethanolamine is injected to block unreacted groups. For kinetics measurements, two-fold serial dilutions of Fab (0.78 nM to 500 nM) are injected in PBS with 0.05% polysorbate 20 (TWEEN-20™) surfactant (PBST) at 25° C. at a flow rate of approximately 25 μl/min. Association rates (k_(on)) and dissociation rates (k_(off)) are calculated using a simple one-to-one Langmuir binding model (BIACORE® Evaluation Software version 3.2) by simultaneously fitting the association and dissociation sensorgrams. The equilibrium dissociation constant (Kd) is calculated as the ratio k_(off)/k_(on) See, e.g., Chen et al., J. Mol. Biol. 293:865-881 (1999). If the on-rate exceeds 10⁶ M⁻¹ s⁻¹ by the surface plasmon resonance assay above, then the on-rate can be determined by using a fluorescent quenching technique that measures the increase or decrease in fluorescence emission intensity (excitation=295 nm; emission=340 nm, 16 nm band-pass) at 25° C. of a 20 nM anti-antigen antibody (Fab form) in PBS, pH 7.2, in the presence of increasing concentrations of antigen as measured in a spectrometer, such as a stop-flow equipped spectrophometer (Aviv Instruments) or a 8000-series SLM-AMINCO™ spectrophotometer (ThermoSpectronic) with a stirred cuvette.

2. Antibody Fragments

In certain embodiments, an antibody provided herein is an antibody fragment. Antibody fragments include, but are not limited to, Fab, Fab′, Fab′-SH, F(ab′)₂, Fv, and scFv fragments, and other fragments described below. For a review of certain antibody fragments, see Hudson et al. Nat. Med. 9:129-134 (2003). For a review of scFv fragments, see, e.g., Pluckthün, in The Pharmacology of Monoclonal Antibodies, vol. 113, Rosenburg and Moore eds., (Springer-Verlag, New York), pp. 269-315 (1994); see also WO 93/16185; and U.S. Pat. Nos. 5,571,894 and 5,587,458. For discussion of Fab and F(ab′)₂ fragments comprising salvage receptor binding epitope residues and having increased in vivo half-life, see U.S. Pat. No. 5,869,046.

Diabodies are antibody fragments with two antigen-binding sites that may be bivalent or bispecific. See, for example, EP 404,097; WO 1993/01161; Hudson et al., Nat. Med. 9:129-134 (2003); and Hollinger et al., Proc. Natl. Acad. Sci. USA 90: 6444-6448 (1993). Triabodies and tetrabodies are also described in Hudson et al., Nat. Med. 9:129-134 (2003).

Single-domain antibodies are antibody fragments comprising all or a portion of the heavy chain variable domain or all or a portion of the light chain variable domain of an antibody. In certain embodiments, a single-domain antibody is a human single-domain antibody (Domantis, Inc., Waltham, Mass.; see, e.g., U.S. Pat. No. 6,248,516 B1).

Antibody fragments can be made by various techniques, including but not limited to proteolytic digestion of an intact antibody as well as production by recombinant host cells (e.g. E. coli or phage), as described herein.

3. Chimeric and Humanized Antibodies

In certain embodiments, an antibody provided herein is a chimeric antibody. Certain chimeric antibodies are described, e.g., in U.S. Pat. No. 4,816,567; and Morrison et al., Proc. Natl. Acad. Sci. USA, 81:6851-6855 (1984)). In one example, a chimeric antibody comprises a non-human variable region (e.g., a variable region derived from a mouse, rat, hamster, rabbit, or non-human primate, such as a monkey) and a human constant region. In a further example, a chimeric antibody is a “class switched” antibody in which the class or subclass has been changed from that of the parent antibody. Chimeric antibodies include antigen-binding fragments thereof.

In certain embodiments, a chimeric antibody is a humanized antibody. Typically, a non-human antibody is humanized to reduce immunogenicity to humans, while retaining the specificity and affinity of the parental non-human antibody. Generally, a humanized antibody comprises one or more variable domains in which HVRs, e.g., CDRs, (or portions thereof) are derived from a non-human antibody, and FRs (or portions thereof) are derived from human antibody sequences. A humanized antibody optionally will also comprise at least a portion of a human constant region. In some embodiments, some FR residues in a humanized antibody are substituted with corresponding residues from a non-human antibody (e.g., the antibody from which the HVR residues are derived), e.g., to restore or improve antibody specificity or affinity.

Humanized antibodies and methods of making them are reviewed, e.g., in Almagro and Fransson, Front. Biosci. 13:1619-1633 (2008), and are further described, e.g., in Riechmann et al., Nature 332:323-329 (1988); Queen et al., Proc. Nat'l Acad. Sci. USA 86:10029-10033 (1989); U.S. Pat. Nos. 5,821,337, 7,527,791, 6,982,321, and 7,087,409; Kashmiri et al., Methods 36:25-34 (2005) (describing SDR (a-CDR) grafting); Padlan, Mol. Immunol. 28:489-498 (1991) (describing “resurfacing”); Dall'Acqua et al., Methods 36:43-60 (2005) (describing “FR shuffling”); and Osbourn et al., Methods 36:61-68 (2005) and Klimka et al., Br. J. Cancer, 83:252-260 (2000) (describing the “guided selection” approach to FR shuffling).

Human framework regions that may be used for humanization include but are not limited to: framework regions selected using the “best-fit” method (see, e.g., Sims et al. J. Immunol. 151:2296 (1993)); framework regions derived from the consensus sequence of human antibodies of a particular subgroup of light or heavy chain variable regions (see, e.g., Carter et al. Proc. Natl. Acad. Sci. USA, 89:4285 (1992); and Presta et al. J. Immunol., 151:2623 (1993)); human mature (somatically mutated) framework regions or human germline framework regions (see, e.g., Almagro and Fransson, Front. Biosci. 13:1619-1633 (2008)); and framework regions derived from screening FR libraries (see, e.g., Baca et al., J. Biol. Chem. 272:10678-10684 (1997) and Rosok et al., J. Biol. Chem. 271:22611-22618 (1996)).

4. Human Antibodies

In certain embodiments, an antibody provided herein is a human antibody. Human antibodies can be produced using various techniques known in the art. Human antibodies are described generally in van Dijk and van de Winkel, Curr. Opin. Pharmacol. 5: 368-74 (2001) and Lonberg, Curr. Opin. Immunol. 20:450-459 (2008).

Human antibodies may be prepared by administering an immunogen to a transgenic animal that has been modified to produce intact human antibodies or intact antibodies with human variable regions in response to antigenic challenge. Such animals typically contain all or a portion of the human immunoglobulin loci, which replace the endogenous immunoglobulin loci, or which are present extrachromosomally or integrated randomly into the animal's chromosomes. In such transgenic mice, the endogenous immunoglobulin loci have generally been inactivated. For review of methods for obtaining human antibodies from transgenic animals, see Lonberg, Nat. Biotech. 23:1117-1125 (2005). See also, e.g., U.S. Pat. Nos. 6,075,181 and 6,150,584 describing XENOMOUSE™ technology; U.S. Pat. No. 5,770,429 describing HUMAB® technology; U.S. Pat. No. 7,041,870 describing K-M MOUSE® technology, and U.S. Patent Application Publication No. US 2007/0061900, describing VELOCIMOUSE® technology). Human variable regions from intact antibodies generated by such animals may be further modified, e.g., by combining with a different human constant region.

Human antibodies can also be made by hybridoma-based methods. Human myeloma and mouse-human heteromyeloma cell lines for the production of human monoclonal antibodies have been described. (See, e.g., Kozbor J. Immunol., 133: 3001 (1984); Brodeur et al., Monoclonal Antibody Production Techniques and Applications, pp. 51-63 (Marcel Dekker, Inc., New York, 1987); and Boerner et al., J. Immunol., 147: 86 (1991).) Human antibodies generated via human B-cell hybridoma technology are also described in Li et al., Proc. Natl. Acad. Sci. USA, 103:3557-3562 (2006). Additional methods include those described, for example, in U.S. Pat. No. 7,189,826 (describing production of monoclonal human IgM antibodies from hybridoma cell lines) and Ni, Xiandai Mianyixue, 26(4):265-268 (2006) (describing human-human hybridomas). Human hybridoma technology (Trioma technology) is also described in Vollmers and Brandlein, Histology and Histopathology, 20(3):927-937 (2005) and Vollmers and Brandlein, Methods and Findings in Experimental and Clinical Pharmacology, 27(3):185-91 (2005).

Human antibodies may also be generated by isolating Fv clone variable domain sequences selected from human-derived phage display libraries. Such variable domain sequences may then be combined with a desired human constant domain. Techniques for selecting human antibodies from antibody libraries are described below.

5. Library-Derived Antibodies

Antibodies of the invention may be isolated by screening combinatorial libraries for antibodies with the desired activity or activities. For example, a variety of methods are known in the art for generating phage display libraries and screening such libraries for antibodies possessing the desired binding characteristics. Such methods are reviewed, e.g., in Hoogenboom et al. in Methods in Molecular Biology 178:1-37 (O'Brien et al., ed., Human Press, Totowa, N.J., 2001) and further described, e.g., in the McCafferty et al., Nature 348:552-554; Clackson et al., Nature 352: 624-628 (1991); Marks et al., J. Mol. Biol. 222: 581-597 (1992); Marks and Bradbury, in Methods in Molecular Biology 248:161-175 (Lo, ed., Human Press, Totowa, N.J., 2003); Sidhu et al., J. Mol. Biol. 338(2): 299-310 (2004); Lee et al., J. Mol. Biol. 340(5): 1073-1093 (2004); Fellouse, Proc. Natl. Acad. Sci. USA 101(34): 12467-12472 (2004); and Lee et al., J. Immunol. Methods 284(1-2): 119-132(2004).

In certain phage display methods, repertoires of VH and VL genes are separately cloned by polymerase chain reaction (PCR) and recombined randomly in phage libraries, which can then be screened for antigen-binding phage as described in Winter et al., Ann. Rev. Immunol., 12: 433-455 (1994). Phage typically display antibody fragments, either as single-chain Fv (scFv) fragments or as Fab fragments. Libraries from immunized sources provide high-affinity antibodies to the immunogen without the requirement of constructing hybridomas. Alternatively, the naive repertoire can be cloned (e.g., from human) to provide a single source of antibodies to a wide range of non-self and also self antigens without any immunization as described by Griffiths et al., EMBO J, 12: 725-734 (1993). Finally, naive libraries can also be made synthetically by cloning unrearranged V-gene segments from stem cells, and using PCR primers containing random sequence to encode the highly variable CDR3 regions and to accomplish rearrangement in vitro, as described by Hoogenboom and Winter, J. Mol. Biol., 227: 381-388 (1992). Patent publications describing human antibody phage libraries include, for example: U.S. Pat. No. 5,750,373, and US Patent Publication Nos. 2005/0079574, 2005/0119455, 2005/0266000, 2007/0117126, 2007/0160598, 2007/0237764, 2007/0292936, and 2009/0002360.

Antibodies or antibody fragments isolated from human antibody libraries are considered human antibodies or human antibody fragments herein.

6. Multispecific Antibodies

In certain embodiments, an antibody provided herein is a multispecific antibody, e.g. a bispecific antibody. Multispecific antibodies are monoclonal antibodies that have binding specificities for at least two different sites. In certain embodiments, one of the binding specificities is for HER2 and the other is for any other antigen. In certain embodiments, one of the binding specificities is for HER2 and the other is for CD3. See, e.g.,U.S. Pat. No. 5,821,337. In certain embodiments, bispecific antibodies may bind to two different epitopes of HER2. Bispecific antibodies may also be used to localize cytotoxic agents to cells which express HER2. Bispecific antibodies can be prepared as full length antibodies or antibody fragments.

Techniques for making multispecific antibodies include, but are not limited to, recombinant co-expression of two immunoglobulin heavy chain-light chain pairs having different specificities (see Milstein and Cuello, Nature 305: 537 (1983)), WO 93/08829, and Traunecker et al., EMBO J. 10: 3655 (1991)), and “knob-in-hole” engineering (see, e.g., U.S. Pat. No. 5,731,168). The term “knob-into-hole” or “KnH” technology as used herein refers to the technology directing the pairing of two polypeptides together in vitro or in vivo by introducing a protuberance (knob) into one polypeptide and a cavity (hole) into the other polypeptide at an interface in which they interact. For example, KnHs have been introduced in the Fc:Fc binding interfaces, CL:CH1 interfaces or VH/VL interfaces of antibodies (see, e.g., US 2011/0287009, US2007/0178552, WO 96/027011, WO 98/050431, Zhu et al., 1997, Protein Science 6:781-788, and WO2012/106587). In some embodiments, KnHs drive the pairing of two different heavy chains together during the manufacture of multispecific antibodies. For example, multispecific antibodies having KnH in their Fc regions can further comprise single variable domains linked to each Fc region, or further comprise different heavy chain variable domains that pair with similar or different light chain variable domains. KnH technology can be also be used to pair two different receptor extracellular domains together or any other polypeptide sequences that comprises different target recognition sequences (e.g., including affibodies, peptibodies and other Fc fusions).

The term “knob mutation” as used herein refers to a mutation that introduces a protuberance (knob) into a polypeptide at an interface in which the polypeptide interacts with another polypeptide. In some embodiments, the other polypeptide has a hole mutation.

The term “hole mutation” as used herein refers to a mutation that introduces a cavity (hole) into a polypeptide at an interface in which the polypeptide interacts with another polypeptide. In some embodiments, the other polypeptide has a knob mutation.

A brief nonlimiting discussion is provided below.

A “protuberance” refers to at least one amino acid side chain which projects from the interface of a first polypeptide and is therefore positionable in a compensatory cavity in the adjacent interface (i.e. the interface of a second polypeptide) so as to stabilize the heteromultimer, and thereby favor heteromultimer formation over homomultimer formation, for example. The protuberance may exist in the original interface or may be introduced synthetically (e.g., by altering nucleic acid encoding the interface). In some embodiments, nucleic acid encoding the interface of the first polypeptide is altered to encode the protuberance. To achieve this, the nucleic acid encoding at least one “original” amino acid residue in the interface of the first polypeptide is replaced with nucleic acid encoding at least one “import” amino acid residue which has a larger side chain volume than the original amino acid residue. It will be appreciated that there can be more than one original and corresponding import residue. The side chain volumes of the various amino residues are shown, for example, in Table 1 of US2011/0287009. A mutation to introduce a “protuberance” may be referred to as a “knob mutation.”

In some embodiments, import residues for the formation of a protuberance are naturally occurring amino acid residues selected from arginine (R), phenylalanine (F), tyrosine (Y) and tryptophan (W). In some embodiments, an import residue is tryptophan or tyrosine. In some embodiment, the original residue for the formation of the protuberance has a small side chain volume, such as alanine, asparagine, aspartic acid, glycine, serine, threonine or valine.

A “cavity” refers to at least one amino acid side chain which is recessed from the interface of a second polypeptide and therefore accommodates a corresponding protuberance on the adjacent interface of a first polypeptide. The cavity may exist in the original interface or may be introduced synthetically (e.g. by altering nucleic acid encoding the interface). In some embodiments, nucleic acid encoding the interface of the second polypeptide is altered to encode the cavity. To achieve this, the nucleic acid encoding at least one “original” amino acid residue in the interface of the second polypeptide is replaced with DNA encoding at least one “import” amino acid residue which has a smaller side chain volume than the original amino acid residue. It will be appreciated that there can be more than one original and corresponding import residue. In some embodiments, import residues for the formation of a cavity are naturally occurring amino acid residues selected from alanine (A), serine (S), threonine (T) and valine (V). In some embodiments, an import residue is serine, alanine or threonine. In some embodiments, the original residue for the formation of the cavity has a large side chain volume, such as tyrosine, arginine, phenylalanine or tryptophan. A mutation to introduce a “cavity” may be referred to as a “hole mutation.”

The protuberance is “positionable” in the cavity which means that the spatial location of the protuberance and cavity on the interface of a first polypeptide and second polypeptide respectively and the sizes of the protuberance and cavity are such that the protuberance can be located in the cavity without significantly perturbing the normal association of the first and second polypeptides at the interface. Since protuberances such as Tyr, Phe and Trp do not typically extend perpendicularly from the axis of the interface and have preferred conformations, the alignment of a protuberance with a corresponding cavity may, in some instances, rely on modeling the protuberance/cavity pair based upon a three-dimensional structure such as that obtained by X-ray crystallography or nuclear magnetic resonance (NMR). This can be achieved using widely accepted techniques in the art.

In some embodiments, a knob mutation in an IgG1 constant region is T366W (EU numbering). In some embodiments, a hole mutation in an IgG1 constant region comprises one or more mutations selected from T366S, L368A and Y407V (EU numbering). In some embodiments, a hole mutation in an IgG1 constant region comprises T366S, L368A and Y407V (EU numbering).

In some embodiments, a knob mutation in an IgG4 constant region is T366W (EU numbering). In some embodiments, a hole mutation in an IgG4 constant region comprises one or more mutations selected from T366S, L368A, and Y407V (EU numbering). In some embodiments, a hole mutation in an IgG4 constant region comprises T366S, L368A, and Y407V (EU numbering).

Multi-specific antibodies may also be made by engineering electrostatic steering effects for making antibody Fc-heterodimeric molecules (WO 2009/089004A1); cross-linking two or more antibodies or fragments (see, e.g., U.S. Pat. No. 4,676,980, and Brennan et al., Science, 229: 81 (1985)); using leucine zippers to produce bi-specific antibodies (see, e.g., Kostelny et al., J. Immunol., 148(5):1547-1553 (1992)); using “diabody” technology for making bispecific antibody fragments (see, e.g., Hollinger et al., Proc. Natl. Acad. Sci. USA, 90:6444-6448 (1993)); and using single-chain Fv (sFv) dimers (see, e.g. Gruber et al., J. Immunol., 152:5368 (1994)); and preparing trispecific antibodies as described, e.g., in Tutt et al. J. Immunol. 147: 60 (1991).

Engineered antibodies with three or more functional antigen binding sites, including “Octopus antibodies,” are also included herein (see, e.g. US 2006/0025576A1).

The antibody or fragment herein also includes a “Dual Acting FAb” or “DAF” comprising an antigen binding site that binds to HER2 as well as another, different antigen (see, US 2008/0069820, for example).

7. Antibody Variants

In certain embodiments, amino acid sequence variants of the antibodies provided herein are contemplated. For example, it may be desirable to improve the binding affinity and/or other biological properties of the antibody. Amino acid sequence variants of an antibody may be prepared by introducing appropriate modifications into the nucleotide sequence encoding the antibody, or by peptide synthesis. Such modifications include, for example, deletions from, and/or insertions into and/or substitutions of residues within the amino acid sequences of the antibody. Any combination of deletion, insertion, and substitution can be made to arrive at the final construct, provided that the final construct possesses the desired characteristics, e.g., antigen-binding.

a) Substitution, Insertion, and Deletion Variants

In certain embodiments, antibody variants having one or more amino acid substitutions are provided. Sites of interest for substitutional mutagenesis include the HVRs and FRs. Conservative substitutions are shown in Table 1 under the heading of “preferred substitutions.” More substantial changes are provided in Table 1 under the heading of “exemplary substitutions,” and as further described below in reference to amino acid side chain classes. Amino acid substitutions may be introduced into an antibody of interest and the products screened for a desired activity, e.g., retained/improved antigen binding, decreased immunogenicity, or improved ADCC or CDC.

TABLE 1 Original Exemplary Preferred Residue Substitutions Substitutions Ala (A) Val; Leu; Ile Val Arg (R) Lys; Gln; Asn Lys Asn (N) Gln; His; Asp, Lys; Arg Gln Asp (D) Glu; Asn Glu Cys (C) Ser; Ala Ser Gln (Q) Asn; Glu Asn Glu (E) Asp; Gln Asp Gly (G) Ala Ala His (H) Asn; Gln; Lys; Arg Arg Ile (I) Leu; Val; Met; Ala; Phe; Norleucine Leu Leu (L) Norleucine; Ile; Val; Met; Ala; Phe Ile Lys (K) Arg; Gln; Asn Arg Met (M) Leu; Phe; Ile Leu Phe (F) Trp; Leu; Val; Ile; Ala; Tyr Tyr Pro (P) Ala Ala Ser (S) Thr Thr Thr (T) Val; Ser Ser Trp (W) Tyr; Phe Tyr Tyr (Y) Trp; Phe; Thr; Ser Phe Val (V) Ile; Leu; Met; Phe; Ala; Norleucine Leu Amino acids may be grouped according to common side-chain properties:

-   -   (1) hydrophobic: Norleucine, Met, Ala, Val, Leu, Ile;     -   (2) neutral hydrophilic: Cys, Ser, Thr, Asn, Gln;     -   (3) acidic: Asp, Glu;     -   (4) basic: His, Lys, Arg;     -   (5) residues that influence chain orientation: Gly, Pro;     -   (6) aromatic: Trp, Tyr, Phe.

Non-conservative substitutions will entail exchanging a member of one of these classes for another class.

One type of substitutional variant involves substituting one or more hypervariable region residues of a parent antibody (e.g. a humanized or human antibody). Generally, the resulting variant(s) selected for further study will have modifications (e.g., improvements) in certain biological properties (e.g., increased affinity, reduced immunogenicity) relative to the parent antibody and/or will have substantially retained certain biological properties of the parent antibody. An exemplary substitutional variant is an affinity matured antibody, which may be conveniently generated, e.g., using phage display-based affinity maturation techniques such as those described herein. Briefly, one or more HVR residues are mutated and the variant antibodies displayed on phage and screened for a particular biological activity (e.g. binding affinity).

Alterations (e.g., substitutions) may be made in HVRs, e.g., to improve antibody affinity. Such alterations may be made in HVR “hotspots,” i.e., residues encoded by codons that undergo mutation at high frequency during the somatic maturation process (see, e.g., Chowdhury, Methods Mol. Biol. 207:179-196 (2008)), and/or SDRs (a-CDRs), with the resulting variant VH or VL being tested for binding affinity. Affinity maturation by constructing and reselecting from secondary libraries has been described, e.g., in Hoogenboom et al. in Methods in Molecular Biology 178:1-37 (O'Brien et al., ed., Human Press, Totowa, N.J., (2001).) In some embodiments of affinity maturation, diversity is introduced into the variable genes chosen for maturation by any of a variety of methods (e.g., error-prone PCR, chain shuffling, or oligonucleotide-directed mutagenesis). A secondary library is then created. The library is then screened to identify any antibody variants with the desired affinity. Another method to introduce diversity involves HVR-directed approaches, in which several HVR residues (e.g., 4-6 residues at a time) are randomized. HVR residues involved in antigen binding may be specifically identified, e.g., using alanine scanning mutagenesis or modeling. CDR-H3 and CDR-L3 in particular are often targeted.

In certain embodiments, substitutions, insertions, or deletions may occur within one or more HVRs so long as such alterations do not substantially reduce the ability of the antibody to bind antigen. For example, conservative alterations (e.g., conservative substitutions as provided herein) that do not substantially reduce binding affinity may be made in HVRs. Such alterations may be outside of HVR “hotspots” or SDRs. In certain embodiments of the variant VH and VL sequences provided above, each HVR either is unaltered, or contains no more than one, two or three amino acid substitutions.

A useful method for identification of residues or regions of an antibody that may be targeted for mutagenesis is called “alanine scanning mutagenesis” as described by Cunningham and Wells (1989) Science, 244:1081-1085. In this method, a residue or group of target residues (e.g., charged residues such as arg, asp, his, lys, and glu) are identified and replaced by a neutral or negatively charged amino acid (e.g., alanine or polyalanine) to determine whether the interaction of the antibody with antigen is affected. Further substitutions may be introduced at the amino acid locations demonstrating functional sensitivity to the initial substitutions. Alternatively, or additionally, a crystal structure of an antigen-antibody complex is used to identify contact points between the antibody and antigen. Such contact residues and neighboring residues may be targeted or eliminated as candidates for substitution. Variants may be screened to determine whether they contain the desired properties.

Amino acid sequence insertions include amino- and/or carboxyl-terminal fusions ranging in length from one residue to polypeptides containing a hundred or more residues, as well as intrasequence insertions of single or multiple amino acid residues. Examples of terminal insertions include an antibody with an N-terminal methionyl residue. Other insertional variants of the antibody molecule include the fusion to the N- or C-terminus of the antibody to an enzyme (e.g. for ADEPT) or a polypeptide which increases the serum half-life of the antibody.

b) Glycosylation Variants

In certain embodiments, an antibody provided herein is altered to increase or decrease the extent to which the antibody is glycosylated. Addition or deletion of glycosylation sites to an antibody may be conveniently accomplished by altering the amino acid sequence such that one or more glycosylation sites is created or removed.

Where the antibody comprises an Fc region, the carbohydrate attached thereto may be altered. Native antibodies produced by mammalian cells typically comprise a branched, biantennary oligosaccharide that is generally attached by an N-linkage to Asn297 of the CH2 domain of the Fc region. See, e.g., Wright et al. TIBTECH 15:26-32 (1997). The oligosaccharide may include various carbohydrates, e.g., mannose, N-acetyl glucosamine (GlcNAc), galactose, and sialic acid, as well as a fucose attached to a GlcNAc in the “stem” of the biantennary oligosaccharide structure. In some embodiments, modifications of the oligosaccharide in an antibody of the invention may be made in order to create antibody variants with certain improved properties.

In one embodiment, antibody variants are provided having a carbohydrate structure that lacks fucose attached (directly or indirectly) to an Fc region. For example, the amount of fucose in such antibody may be from 1% to 80%, from 1% to 65%, from 5% to 65% or from 20% to 40%. The amount of fucose is determined by calculating the average amount of fucose within the sugar chain at Asn297, relative to the sum of all glycostructures attached to Asn 297 (e. g. complex, hybrid and high mannose structures) as measured by MALDI-TOF mass spectrometry, as described in WO 2008/077546, for example. Asn297 refers to the asparagine residue located at about position 297 in the Fc region (Eu numbering of Fc region residues); however, Asn297 may also be located about ±3 amino acids upstream or downstream of position 297, i.e., between positions 294 and 300, due to minor sequence variations in antibodies. Such fucosylation variants may have improved ADCC function. See, e.g., US Patent Publication Nos. US 2003/0157108 (Presta, L.); US 2004/0093621 (Kyowa Hakko Kogyo Co., Ltd). Examples of publications related to “defucosylated” or “fucose-deficient” antibody variants include: US 2003/0157108; WO 2000/61739; WO 2001/29246; US 2003/0115614; US 2002/0164328; US 2004/0093621; US 2004/0132140; US 2004/0110704; US 2004/0110282; US 2004/0109865; WO 2003/085119; WO 2003/084570; WO 2005/035586; WO 2005/035778; WO2005/053742; WO2002/031140; Okazaki et al. J. Mol. Biol. 336:1239-1249 (2004); Yamane-Ohnuki et al. Biotech. Bioeng. 87: 614 (2004). Examples of cell lines capable of producing defucosylated antibodies include Lec13 CHO cells deficient in protein fucosylation (Ripka et al. Arch. Biochem. Biophys. 249:533-545 (1986); US Pat Appl No US 2003/0157108 A1, Presta, L; and WO 2004/056312 A1, Adams et al., especially at Example 11), and knockout cell lines, such as alpha-1,6-fucosyltransferase gene, FUT8, knockout CHO cells (see, e.g., Yamane-Ohnuki et al. Biotech. Bioeng. 87: 614 (2004); Kanda, Y. et al., Biotechnol. Bioeng., 94(4):680-688 (2006); and WO2003/085107).

Antibodies variants are further provided with bisected oligosaccharides, e.g., in which a biantennary oligosaccharide attached to the Fc region of the antibody is bisected by GlcNAc. Such antibody variants may have reduced fucosylation and/or improved ADCC function. Examples of such antibody variants are described, e.g., in WO 2003/011878 (Jean-Mairet et al.); U.S. Pat. No. 6,602,684 (Umana et al.); and US 2005/0123546 (Umana et al.). Antibody variants with at least one galactose residue in the oligosaccharide attached to the Fc region are also provided. Such antibody variants may have improved CDC function. Such antibody variants are described, e.g., in WO 1997/30087 (Patel et al.); WO 1998/58964 (Raju, S.); and WO 1999/22764 (Raju, S.).

c) Fc Region Variants

In certain embodiments, one or more amino acid modifications may be introduced into the Fc region of an antibody provided herein, thereby generating an Fc region variant. The Fc region variant may comprise a human Fc region sequence (e.g., a human IgG1, IgG2, IgG3 or IgG4 Fc region) comprising an amino acid modification (e.g. a substitution) at one or more amino acid positions.

In certain embodiments, the invention contemplates an antibody variant that possesses some but not all effector functions, which make it a desirable candidate for applications in which the half life of the antibody in vivo is important yet certain effector functions (such as complement and ADCC) are unnecessary or deleterious. In vitro and/or in vivo cytotoxicity assays can be conducted to confirm the reduction/depletion of CDC and/or ADCC activities. For example, Fc receptor (FcR) binding assays can be conducted to ensure that the antibody lacks FcγR binding (hence likely lacking ADCC activity), but retains FcRn binding ability. The primary cells for mediating ADCC, NK cells, express Fc(RIII only, whereas monocytes express Fc(RI, Fc(RII and Fc(RIII FcR expression on hematopoietic cells is summarized in Table 3 on page 464 of Ravetch and Kinet, Annu. Rev. Immunol. 9:457-492 (1991). Non-limiting examples of in vitro assays to assess ADCC activity of a molecule of interest is described in U.S. Pat. No. 5,500,362 (see, e.g. Hellstrom, I. et al. Proc. Nat'l Acad. Sci. USA 83:7059-7063 (1986)) and Hellstrom, I et al., Proc. Nat'l Acad. Sci. USA 82:1499-1502 (1985); 5,821,337 (see Bruggemann, M. et al., J. Exp. Med. 166:1351-1361 (1987)). Alternatively, non-radioactive assays methods may be employed (see, for example, ACTI™ non-radioactive cytotoxicity assay for flow cytometry (CellTechnology, Inc. Mountain View, Calif.; and CytoTox 96® non-radioactive cytotoxicity assay (Promega, Madison, Wis.). Useful effector cells for such assays include peripheral blood mononuclear cells (PBMC) and Natural Killer (NK) cells. Alternatively, or additionally, ADCC activity of the molecule of interest may be assessed in vivo, e.g., in a animal model such as that disclosed in Clynes et al. Proc. Nat'l Acad. Sci. USA 95:652-656 (1998). C1q binding assays may also be carried out to confirm that the antibody is unable to bind C1q and hence lacks CDC activity. See, e.g., C1q and C3c binding ELISA in WO 2006/029879 and WO 2005/100402. To assess complement activation, a CDC assay may be performed (see, for example, Gazzano-Santoro et al., J. Immunol. Methods 202:163 (1996); Cragg, M. S. et al., Blood 101:1045-1052 (2003); and Cragg, M. S. and M. J. Glennie, Blood 103:2738-2743 (2004)). FcRn binding and in vivo clearance/half life determinations can also be performed using methods known in the art (see, e.g., Petkova, S. B. et al., Int'l. Immunol. 18(12):1759-1769 (2006)).

In some embodiments, one or more amino acid modifications may be introduced into the Fc portion of the antibody provided herein in order to increase IgG binding to the neonatal Fc receptor. In certain embodiments, the antibody comprises the following three mutations according to EU numbering: M252Y, S254T, and T256E (the “YTE mutation”) (U.S. Pat. No. 8,697,650; see also Dall'Acqua et al., Journal of Biological Chemistry 281(33):23514-23524 (2006). In certain embodiments, the YTE mutation does not affect the ability of the antibody to bind to its cognate antigen. In certain embodiments, the YTE mutation increases the antibody's serum half-life compared to the native (i.e., non-YTE mutant) antibody. In some embodiments, the YTE mutation increases the serum half-life of the antibody by 3-fold compared to the native (i.e., non-YTE mutant) antibody. In some embodiments, the YTE mutation increases the serum half-life of the antibody by 2-fold compared to the native (i.e., non-YTE mutant) antibody. In some embodiments, the YTE mutation increases the serum half-life of the antibody by 4-fold compared to the native (i.e., non-YTE mutant) antibody. In some embodiments, the YTE mutation increases the serum half-life of the antibody by at least 5-fold compared to the native (i.e., non-YTE mutant) antibody. In some embodiments, the YTE mutation increases the serum half-life of the antibody by at least 10-fold compared to the native (i.e., non-YTE mutant) antibody. See, e.g., U.S. Pat. No. 8,697,650; see also Dall'Acqua et al., Journal of Biological Chemistry 281(33):23514-23524 (2006).

In certain embodiments, the YTE mutant provides a means to modulate antibody-dependent cell-mediated cytotoxicity (ADCC) activity of the antibody. In certain embodiments, the YTEO mutant provides a means to modulate ADCC activity of a humanized IgG antibody directed against a human antigen. See, e.g., U.S. Pat. No. 8,697,650; see also Dall'Acqua et al., Journal of Biological Chemistry 281(33):23514-23524 (2006).

In certain embodiments, the YTE mutant allows the simultaneous modulation of serum half-life, tissue distribution, and antibody activity (e.g., the ADCC activity of an IgG antibody). See, e.g., U.S. Pat. No. 8,697,650; see also Dall'Acqua et al., Journal of Biological Chemistry 281(33):23514-23524 (2006).

Antibodies with reduced effector function include those with substitution of one or more of Fc region residues 238, 265, 269, 270, 297, 327 and 329 (U.S. Pat. No. 6,737,056). Such Fc mutants include Fc mutants with substitutions at two or more of amino acid positions 265, 269, 270, 297 and 327, including the so-called “DANA” Fc mutant with substitution of residues 265 and 297 to alanine (U.S. Pat. No. 7,332,581).

In certain embodiments, the proline at position 329 (EU numbering) (P329) of a wild-type human Fc region is substituted with glycine or arginine or an amino acid residue large enough to destroy the proline sandwich within the Fc/Fc□ receptor interface, that is formed between the P329 of the Fc and tryptophane residues W87 and W110 of FcgRIII (Sondermann et al.: Nature 406, 267-273 (20 Jul. 2000)). In a further embodiment, at least one further amino acid substitution in the Fc variant is S228P, E233P, L234A, L235A, L235E, N297A, N297D, or P331S and still in another embodiment said at least one further amino acid substitution is L234A and L235A of the human IgG1 Fc region or S228P and L235E of the human IgG4 Fc region, all according to EU numbering (U.S. Pat. No. 8,969,526 which is incorporated by reference in its entirety).

In certain embodiments, a polypeptide comprises the Fc variant of a wild-type human IgG Fc region wherein the polypeptide has P329 of the human IgG Fc region substituted with glycine and wherein the Fc variant comprises at least two further amino acid substitutions at L234A and L235A of the human IgG1 Fc region or S228P and L235E of the human IgG4 Fc region, and wherein the residues are numbered according to the EU numbering (U.S. Pat. No. 8,969,526 which is incorporated by reference in its entirety). In certain embodiments, the polypeptide comprising the P329G, L234A and L235A (EU numbering) substitutions exhibit a reduced affinity to the human FcγRIIIA and FcγRIIA, for down-modulation of ADCC to at least 20% of the ADCC induced by the polypeptide comprising the wildtype human IgG Fc region, and/or for down-modulation of ADCP (U.S. Pat. No. 8,969,526 which is incorporated by reference in its entirety).

In a specific embodiment the polypeptide comprising an Fc variant of a wildtype human Fc polypeptide comprises a triple mutation: an amino acid substitution at position Pro329, a L234A and a L235A mutation according to EU numbering (P329/LALA) (U.S. Pat. No. 8,969,526 which is incorporated by reference in its entirety). In specific embodiments, the polypeptide comprises the following amino acid substitutions: P329G, L234A, and L235A according to EU numbering.

Certain antibody variants with improved or diminished binding to FcRs are described. (See, e.g., U.S. Pat. No. 6,737,056; WO 2004/056312, and Shields et al., J. Biol. Chem. 9(2): 6591-6604 (2001).)

In certain embodiments, an antibody variant comprises an Fc region with one or more amino acid substitutions which improve ADCC, e.g., substitutions at positions 298, 333, and/or 334 of the Fc region (EU numbering of residues).

In some embodiments, alterations are made in the Fc region that result in altered (i.e., either improved or diminished) C1q binding and/or Complement Dependent Cytotoxicity (CDC), e.g., as described in U.S. Pat. No. 6,194,551, WO 99/51642, and Idusogie et al. J. Immunol. 164: 4178-4184 (2000).

Antibodies with increased half lives and improved binding to the neonatal Fc receptor (FcRn), which is responsible for the transfer of maternal IgGs to the fetus (Guyer et al., J. Immunol. 117:587 (1976) and Kim et al., J. Immunol. 24:249 (1994)), are described in US2005/0014934A1 (Hinton et al.). Those antibodies comprise an Fc region with one or more substitutions therein which improve binding of the Fc region to FcRn. Such Fc variants include those with substitutions at one or more of Fc region residues: 238, 256, 265, 272, 286, 303, 305, 307, 311, 312, 317, 340, 356, 360, 362, 376, 378, 380, 382, 413, 424 or 434, e.g., substitution of Fc region residue 434 (U.S. Pat. No. 7,371,826).

See also Duncan & Winter, Nature 322:738-40 (1988); U.S. Pat. No. 5,648,260; U.S. Pat. No. 5,624,821; and WO 94/29351 concerning other examples of Fc region variants.

d) Cysteine Engineered Antibody Variants

In certain embodiments, it may be desirable to create cysteine engineered antibodies, e.g., a “THIOMAB™,” in which one or more residues of an antibody are substituted with cysteine residues. In particular embodiments, the substituted residues occur at sites of the antibody that are available for conjugation. By substituting those residues with cysteine, reactive thiol groups are thereby positioned at accessible sites of the antibody and may be used to conjugate the antibody to other moieties, such as drug moieties or linker-drug moieties, to create an immunoconjugate, as described further herein. In certain embodiments, any one or more of the following residues may be substituted with cysteine: K149 (Kabat numbering) of the light chain; V205 (Kabat numbering) of the light chain; A118 (EU numbering) of the heavy chain; A140 (EU numbering) of the heavy chain; L174 (EU numbering) of the heavy chain; Y373 (EU numbering) of the heavy chain; and 5400 (EU numbering) of the heavy chain Fc region. In specific embodiments, the antibodies described herein comprise the HC-A140C (EU numbering) cysteine substitution. In specific embodiments, the antibodies described herein comprise the LC-K149C (Kabat numbering) cysteine substitution. In specific embodiments, the antibodies described herein comprise the HC-A118C (EU numbering) cysteine substitution. Cysteine engineered antibodies may be generated as described, e.g., in U.S. Pat. No. 7,521,541.

In certain embodiments, the antibody comprises one of the following heavy chain cysteine substitutions:

Chain EU Mutation Kabat Mutation (HC/LC) Residue Site # Site # HC T 114 110 HC A 140 136 HC L 174 170 HC L 179 175 HC T 187 183 HC T 209 205 HC V 262 258 HC G 371 367 HC Y 373 369 HC E 382 378 HC S 424 420 HC N 434 430 HC Q 438 434

In certain embodiments, the antibody comprises one of the following light chain cysteine substitutions:

Chain EU Mutation Kabat Mutation (HC/LC) Residue Site # Site # LC I 106 106 LC R 108 108 LC R 142 142 LC K 149 149 LC V 205 205

A nonlimiting exemplary hu7C2.v2.2.LA light chain (LC) K149C THIOMAB™ has the heavy chain and light chain amino acid sequences of SEQ ID NOs: 19 and 23, respectively. A nonlimiting exemplary hu7C2.v2.2.LA heavy chain (HC) A118C THIOMAB™ has the heavy chain and light chain amino acid sequences of SEQ ID NOs: 24 and 18, respectively.

An exemplary S400C cysteine engineered heavy chain constant region is shown in SEQ ID NO: 28. The S400C cysteine engineered heavy chain constant region may be fused to the C-terminus of the hu7C2.v2.2.LA heavy chain variable region shown in SEQ ID NO: 11. The resulting hu7C2.v2.2.LA HC S400C heavy chain may be paired with a hu7C2.v2.2.LA kappa light chain, such as the light chain shown in SEQ ID NO: 18.

An exemplary V205C cysteine engineered light chain constant region is shown in SEQ ID NO: 25. The V205C cysteine engineered light chain constant region may be fused to the C-terminus of the hu7C2.v2.2.LA light chain variable region shown in SEQ ID NO: 10. The resulting hu7C2.v2.2.LA LC V205C light chain may be paired with a hu7C2.v2.2.LA IgG heavy chain, such as the heavy chain shown in SEQ ID NO: 19.

-   -   e) Antibody Derivatives

In certain embodiments, an antibody provided herein may be further modified to contain additional nonproteinaceous moieties that are known in the art and readily available. The moieties suitable for derivatization of the antibody include but are not limited to water soluble polymers. Non-limiting examples of water soluble polymers include, but are not limited to, polyethylene glycol (PEG), copolymers of ethylene glycol/propylene glycol, carboxymethylcellulose, dextran, polyvinyl alcohol, polyvinyl pyrrolidone, poly-1, 3-dioxolane, poly-1,3,6-trioxane, ethylene/maleic anhydride copolymer, polyaminoacids (either homopolymers or random copolymers), and dextran or poly(n-vinyl pyrrolidone)polyethylene glycol, propropylene glycol homopolymers, prolypropylene oxide/ethylene oxide co-polymers, polyoxyethylated polyols (e.g., glycerol), polyvinyl alcohol, and mixtures thereof. Polyethylene glycol propionaldehyde may have advantages in manufacturing due to its stability in water. The polymer may be of any molecular weight, and may be branched or unbranched. The number of polymers attached to the antibody may vary, and if more than one polymer are attached, they can be the same or different molecules. In general, the number and/or type of polymers used for derivatization can be determined based on considerations including, but not limited to, the particular properties or functions of the antibody to be improved, whether the antibody derivative will be used in a therapy under defined conditions, etc.

In another embodiment, conjugates of an antibody and nonproteinaceous moiety that may be selectively heated by exposure to radiation are provided. In one embodiment, the nonproteinaceous moiety is a carbon nanotube (Kam et al., Proc. Natl. Acad. Sci. USA 102: 11600-11605 (2005)). The radiation may be of any wavelength, and includes, but is not limited to, wavelengths that do not harm ordinary cells, but which heat the nonproteinaceous moiety to a temperature at which cells proximal to the antibody-nonproteinaceous moiety are killed.

B. Recombinant Methods and Compositions

Antibodies may be produced using recombinant methods and compositions, e.g., as described in U.S. Pat. No. 4,816,567. In one embodiment, isolated nucleic acid encoding an anti-HER2 antibody described herein is provided. Such nucleic acid may encode an amino acid sequence comprising the VL and/or an amino acid sequence comprising the VH of the antibody (e.g., the light and/or heavy chains of the antibody). In a further embodiment, one or more vectors (e.g., expression vectors) comprising such nucleic acid are provided. In a further embodiment, a host cell comprising such nucleic acid is provided. In one such embodiment, a host cell comprises (e.g., has been transformed with): (1) a vector comprising a nucleic acid that encodes an amino acid sequence comprising the VL of the antibody and an amino acid sequence comprising the VH of the antibody, or (2) a first vector comprising a nucleic acid that encodes an amino acid sequence comprising the VL of the antibody and a second vector comprising a nucleic acid that encodes an amino acid sequence comprising the VH of the antibody. In one embodiment, the host cell is eukaryotic, e.g. a Chinese Hamster Ovary (CHO) cell or lymphoid cell (e.g., Y0, NS0, Sp20 cell). In one embodiment, a method of making an anti-HER2 antibody is provided, wherein the method comprises culturing a host cell comprising a nucleic acid encoding the antibody, as provided above, under conditions suitable for expression of the antibody, and optionally recovering the antibody from the host cell (or host cell culture medium).

For recombinant production of an anti-HER2 antibody, nucleic acid encoding an antibody, e.g., as described above, is isolated and inserted into one or more vectors for further cloning and/or expression in a host cell. Such nucleic acid may be readily isolated and sequenced using conventional procedures (e.g., by using oligonucleotide probes that are capable of binding specifically to genes encoding the heavy and light chains of the antibody).

Suitable host cells for cloning or expression of antibody-encoding vectors include prokaryotic or eukaryotic cells described herein. For example, antibodies may be produced in bacteria, in particular when glycosylation and Fc effector function are not needed. For expression of antibody fragments and polypeptides in bacteria, see, e.g., U.S. Pat. Nos. 5,648,237, 5,789,199, and 5,840,523. (See also Charlton, Methods in Molecular Biology, Vol. 248 (B. K. C. Lo, ed., Humana Press, Totowa, N.J., 2003), pp. 245-254, describing expression of antibody fragments in E. coli.) After expression, the antibody may be isolated from the bacterial cell paste in a soluble fraction and can be further purified.

In addition to prokaryotes, eukaryotic microbes such as filamentous fungi or yeast are suitable cloning or expression hosts for antibody-encoding vectors, including fungi and yeast strains whose glycosylation pathways have been “humanized,” resulting in the production of an antibody with a partially or fully human glycosylation pattern. See Gerngross, Nat. Biotech. 22:1409-1414 (2004), and Li et al., Nat. Biotech. 24:210-215 (2006).

Suitable host cells for the expression of glycosylated antibody are also derived from multicellular organisms (invertebrates and vertebrates). Examples of invertebrate cells include plant and insect cells. Numerous baculoviral strains have been identified which may be used in conjunction with insect cells, particularly for transfection of Spodoptera frugiperda cells.

Plant cell cultures can also be utilized as hosts. See, e.g., U.S. Pat. Nos. 5,959,177, 6,040,498, 6,420,548, 7,125,978, and 6,417,429 (describing PLANTIBODIES™ technology for producing antibodies in transgenic plants).

Vertebrate cells may also be used as hosts. For example, mammalian cell lines that are adapted to grow in suspension may be useful. Other examples of useful mammalian host cell lines are monkey kidney CV1 line transformed by SV40 (COS-7); human embryonic kidney line (293 or 293 cells as described, e.g., in Graham et al., J. Gen Virol. 36:59 (1977)); baby hamster kidney cells (BHK); mouse sertoli cells (TM4 cells as described, e.g., in Mather, Biol. Reprod. 23:243-251 (1980)); monkey kidney cells (CV1); African green monkey kidney cells (VERO-76); human cervical carcinoma cells (HELA); canine kidney cells (MDCK; buffalo rat liver cells (BRL 3A); human lung cells (W138); human liver cells (Hep G2); mouse mammary tumor (MMT 060562); TRI cells, as described, e.g., in Mather et al., Annals N.Y. Acad. Sci. 383:44-68 (1982); MRC 5 cells; and FS4 cells. Other useful mammalian host cell lines include Chinese hamster ovary (CHO) cells, including DHFR⁻ CHO cells (Urlaub et al., Proc. Natl. Acad. Sci. USA 77:4216 (1980)); and myeloma cell lines such as Y0, NS0 and Sp2/0. For a review of certain mammalian host cell lines suitable for antibody production, see, e.g., Yazaki and Wu, Methods in Molecular Biology, Vol. 248 (B. K. C. Lo, ed., Humana Press, Totowa, N.J.), pp. 255-268 (2003).

C. Assays

Anti-HER2 antibodies provided herein may be identified, screened for, or characterized for their physical/chemical properties and/or biological activities by various assays known in the art.

In one aspect, an antibody of the invention is tested for its antigen binding activity, e.g., by known methods such as ELISA, BIACore®, FACS, or Western blot.

In another aspect, competition assays may be used to identify an antibody that competes with any of the antibodies described herein for binding to HER2. In certain embodiments, such a competing antibody binds to the same epitope (e.g., a linear or a conformational epitope) that is bound by an antibody described herein. Detailed exemplary methods for mapping an epitope to which an antibody binds are provided in Morris (1996) “Epitope Mapping Protocols,” in Methods in Molecular Biology vol. 66 (Humana Press, Totowa, N.J.).

In an exemplary competition assay, immobilized HER2 is incubated in a solution comprising a first labeled antibody that binds to HER2 (e.g., any of the antibodies described herein) and a second unlabeled antibody that is being tested for its ability to compete with the first antibody for binding to HER2. The second antibody may be present in a hybridoma supernatant. As a control, immobilized HER2 is incubated in a solution comprising the first labeled antibody but not the second unlabeled antibody. After incubation under conditions permissive for binding of the first antibody to HER2, excess unbound antibody is removed, and the amount of label associated with immobilized HER2 is measured. If the amount of label associated with immobilized HER2 is substantially reduced in the test sample relative to the control sample, then that indicates that the second antibody is competing with the first antibody for binding to HER2. See Harlow and Lane (1988) Antibodies: A Laboratory Manual ch.14 (Cold Spring Harbor Laboratory, Cold Spring Harbor, N.Y.).

D. Immunoconjugates

The invention also provides immunoconjugates comprising any anti-HER2 antibody provided herein conjugated to one or more cytotoxic agents, such as chemotherapeutic agents or drugs, growth inhibitory agents, toxins (e.g., protein toxins, enzymatically active toxins of bacterial, fungal, plant, or animal origin, or fragments thereof), or radioactive isotopes (i.e., a radioconjugate).

Immunoconjugates allow for the targeted delivery of a drug moiety to a tumor, and, in some embodiments intracellular accumulation therein, where systemic administration of unconjugated drugs may result in unacceptable levels of toxicity to normal cells (Polakis P. (2005) Current Opinion in Pharmacology 5:382-387).

Antibody-drug conjugates (ADC) are targeted chemotherapeutic molecules which combine properties of both antibodies and cytotoxic drugs by targeting potent cytotoxic drugs to antigen-expressing tumor cells (Teicher, B. A. (2009) Current Cancer Drug Targets 9:982-1004), thereby enhancing the therapeutic index by maximizing efficacy and minimizing off-target toxicity (Carter, P. J. and Senter P. D. (2008) The Cancer Jour. 14(3):154-169; Chari, R. V. (2008) Acc. Chem. Res. 41:98-107.

The ADC compounds of the invention include those with anticancer activity. In some embodiments, the ADC compounds include an antibody conjugated, i.e. covalently attached, to the drug moiety. In some embodiments, the antibody is covalently attached to the drug moiety through a linker. The antibody-drug conjugates (ADC) of the invention selectively deliver an effective dose of a drug to tumor tissue whereby greater selectivity, i.e. a lower efficacious dose, may be achieved while increasing the therapeutic index (“therapeutic window”).

The drug moiety (D) of the antibody-drug conjugates (ADC) may include any compound, moiety or group that has a cytotoxic or cytostatic effect. Drug moieties may impart their cytotoxic and cytostatic effects by mechanisms including but not limited to tubulin binding, DNA binding or intercalation, and inhibition of RNA polymerase, protein synthesis, and/or topoisomerase. Exemplary drug moieties include, but are not limited to, pyrrolobenzodiazepine (PBD), and stereoisomers, isosteres, analogs, and derivatives thereof that have cytotoxic activity. Nonlimiting examples of such immunoconjugates are discussed in further detail below.

1. Exemplary Antibody-Drug Conjugates

An exemplary embodiment of an antibody-drug conjugate (ADC) compound comprises an antibody (Ab) which targets a tumor cell, a drug moiety (D), and a linker moiety (L) that attaches Ab to D. In some embodiments, the antibody is attached to the linker moiety (L) through one or more amino acid residues, such as lysine and/or cysteine.

An exemplary ADC has Formula I:

Ab-(L-D)_(p)  I

where p is 1 to about 20. In some embodiments, the number of drug moieties that can be conjugated to an antibody is limited by the number of free cysteine residues. In some embodiments, free cysteine residues are introduced into the antibody amino acid sequence by the methods described herein. Exemplary ADC of Formula I include, but are not limited to, antibodies that have 1, 2, 3, or 4 engineered cysteine amino acids (Lyon, R. et al (2012) Methods in Enzym. 502:123-138). In some embodiments, one or more free cysteine residues are already present in an antibody, without the use of engineering, in which case the existing free cysteine residues may be used to conjugate the antibody to a drug. In some embodiments, an antibody is exposed to reducing conditions prior to conjugation of the antibody in order to generate one or more free cysteine residues.

a) Exemplary Linkers

A “Linker” (L) is a bifunctional or multifunctional moiety that can be used to link one or more drug moieties (D) to an antibody (Ab) to form an antibody-drug conjugate (ADC) of Formula I. In some embodiments, antibody-drug conjugates (ADC) can be prepared using a Linker having reactive functionalities for covalently attaching to the drug and to the antibody. For example, in some embodiments, a cysteine thiol of an antibody (Ab) can form a bond with a reactive functional group of a linker or a drug-linker intermediate to make an ADC.

In one aspect, a linker has a functionality that is capable of reacting with a free cysteine present on an antibody to form a covalent bond. Nonlimiting exemplary such reactive functionalities include maleimide, haloacetamides, α-haloacetyl, activated esters such as succinimide esters, 4-nitrophenyl esters, pentafluorophenyl esters, tetrafluorophenyl esters, anhydrides, acid chlorides, sulfonyl chlorides, isocyanates, and isothiocyanates. See, e.g., the conjugation method at page 766 of Klussman, et al (2004), Bioconjugate Chemistry 15(4):765-773, and the Examples herein.

In some embodiments, a linker has a functionality that is capable of reacting with an electrophilic group present on an antibody. Exemplary such electrophilic groups include, but are not limited to, aldehyde and ketone carbonyl groups. In some embodiments, a heteroatom of the reactive functionality of the linker can react with an electrophilic group on an antibody and form a covalent bond to an antibody unit. Nonlimiting exemplary such reactive functionalities include, but are not limited to, hydrazide, oxime, amino, hydrazine, thiosemicarbazone, hydrazine carboxylate, and arylhydrazide.

A linker may comprise one or more linker components. Exemplary linker components include 6-maleimidocaproyl (“MC”), maleimidopropanoyl (“MP”), valine-citrulline (“val-cit” or “vc”), alanine-phenylalanine (“ala-phe”), p-aminobenzyloxycarbonyl (a “PAB”), N-Succinimidyl 4-(2-pyridylthio)pentanoate (“SPP”), and 4-(N-maleimidomethyl)cyclohexane-1 carboxylate (“MCC”). Various linker components are known in the art, some of which are described below.

A linker may be a “cleavable linker,” facilitating release of a drug. Nonlimiting exemplary cleavable linkers include acid-labile linkers (e.g., comprising hydrazone), protease-sensitive (e.g., peptidase-sensitive) linkers, photolabile linkers, or disulfide-containing linkers (Chari et al., Cancer Research 52:127-131 (1992); U.S. Pat. No. 5,208,020).

In certain embodiments, a linker has the following Formula II:

-A_(a)-W_(w)—Y_(y)—  II

wherein A is a “stretcher unit”, and a is an integer from 0 to 1; W is an “amino acid unit”, and w is an integer from 0 to 12; Y is a “spacer unit”, and y is 0, 1, or 2; and Ab, D, and p are defined as above for Formula I. Exemplary embodiments of such linkers are described in U.S. Pat. No. 7,498,298, which is expressly incorporated herein by reference.

In some embodiments, a linker component comprises a “stretcher unit” that links an antibody to another linker component or to a drug moiety. Nonlimiting exemplary stretcher units are shown below (wherein the wavy line indicates sites of covalent attachment to an antibody, drug, or additional linker components):

In some embodiments, a linker component comprises an “amino acid unit”. In some such embodiments, the amino acid unit allows for cleavage of the linker by a protease, thereby facilitating release of the drug from the immunoconjugate upon exposure to intracellular proteases, such as lysosomal enzymes (Doronina et al. (2003) Nat. Biotechnol. 21:778-784). Exemplary amino acid units include, but are not limited to, dipeptides, tripeptides, tetrapeptides, and pentapeptides. Exemplary dipeptides include, but are not limited to, valine-citrulline (vc or val-cit), alanine-phenylalanine (af or ala-phe); phenylalanine-lysine (fk or phe-lys); phenylalanine-homolysine (phe-homolys); and N-methyl-valine-citrulline (Me-val-cit). Exemplary tripeptides include, but are not limited to, glycine-valine-citrulline (gly-val-cit) and glycine-glycine-glycine (gly-gly-gly). An amino acid unit may comprise amino acid residues that occur naturally and/or minor amino acids and/or non-naturally occurring amino acid analogs, such as citrulline. Amino acid units can be designed and optimized for enzymatic cleavage by a particular enzyme, for example, a tumor-associated protease, cathepsin B, C and D, or a plasmin protease.

In some embodiments, a linker component comprises a “spacer” unit that links the antibody to a drug moiety, either directly or through a stretcher unit and/or an amino acid unit. A spacer unit may be “self-immolative” or a “non-self-immolative.” A “non-self-immolative” spacer unit is one in which part or all of the spacer unit remains bound to the drug moiety upon cleavage of the ADC. Examples of non-self-immolative spacer units include, but are not limited to, a glycine spacer unit and a glycine-glycine spacer unit. In some embodiments, enzymatic cleavage of an ADC containing a glycine-glycine spacer unit by a tumor-cell associated protease results in release of a glycine-glycine-drug moiety from the remainder of the ADC. In some such embodiments, the glycine-glycine-drug moiety is subjected to a hydrolysis step in the tumor cell, thus cleaving the glycine-glycine spacer unit from the drug moiety.

A “self-immolative” spacer unit allows for release of the drug moiety. In certain embodiments, a spacer unit of a linker comprises a p-aminobenzyl unit. In some such embodiments, a p-aminobenzyl alcohol is attached to an amino acid unit via an amide bond, and a carbamate, methylcarbamate, or carbonate is made between the benzyl alcohol and the drug (Hamann et al. (2005) Expert Opin. Ther. Patents (2005) 15:1087-1103). In some embodiments, the spacer unit is p-aminobenzyloxycarbonyl (PAB). In some embodiments, an ADC comprising a self-immolative linker has the structure:

wherein Q is —C₁-C₈ alkyl, —O—(C₁-C₈ alkyl), -halogen, -nitro, or -cyno; m is an integer ranging from 0 to 4; and p ranges from 1 to about 20. In some embodiments, p ranges from 1 to 10, 1 to 7, 1 to 5, or 1 to 4.

Other examples of self-immolative spacers include, but are not limited to, aromatic compounds that are electronically similar to the PAB group, such as 2-aminoimidazol-5-methanol derivatives (U.S. Pat. No. 7,375,078; Hay et al. (1999) Bioorg. Med. Chem. Lett. 9:2237) and ortho- or para-aminobenzylacetals. In some embodiments, spacers can be used that undergo cyclization upon amide bond hydrolysis, such as substituted and unsubstituted 4-aminobutyric acid amides (Rodrigues et al (1995) Chemistry Biology 2:223), appropriately substituted bicyclo[2.2.1] and bicyclo[2.2.2]ring systems (Storm et al (1972) J. Amer. Chem. Soc. 94:5815) and 2-aminophenylpropionic acid amides (Amsberry, et al (1990) J. Org. Chem. 55:5867). Linkage of a drug to the α-carbon of a glycine residue is another example of a self-immolative spacer that may be useful in ADC (Kingsbury et al (1984) J. Med. Chem. 27:1447).

In some embodiments, linker L may be a dendritic type linker for covalent attachment of more than one drug moiety to an antibody through a branching, multifunctional linker moiety (Sun et al (2002) Bioorganic & Medicinal Chemistry Letters 12:2213-2215; Sun et al (2003) Bioorganic & Medicinal Chemistry 11:1761-1768). Dendritic linkers can increase the molar ratio of drug to antibody, i.e. loading, which is related to the potency of the ADC. Thus, where an antibody bears only one reactive cysteine thiol group, a multitude of drug moieties may be attached through a dendritic linker.

Nonlimiting exemplary linkers are shown below in the context of an ADC of Formula I:

Further nonlimiting exemplary ADCs include the structures:

each R is independently H or C₁-C₆ alkyl; and n is 1 to 12.

Typically, peptide-type linkers can be prepared by forming a peptide bond between two or more amino acids and/or peptide fragments. Such peptide bonds can be prepared, for example, according to a liquid phase synthesis method (e.g., E. Schroder and K. Lübke (1965) “The Peptides”, volume 1, pp 76-136, Academic Press).

In some embodiments, a linker is substituted with groups that modulate solubility and/or reactivity. As a nonlimiting example, a charged substituent such as sulfonate (—SO₃ ⁻) or ammonium may increase water solubility of the linker reagent and facilitate the coupling reaction of the linker reagent with the antibody and/or the drug moiety, or facilitate the coupling reaction of Ab-L (antibody-linker intermediate) with D, or D-L (drug-linker intermediate) with Ab, depending on the synthetic route employed to prepare the ADC. In some embodiments, a portion of the linker is coupled to the antibody and a portion of the linker is coupled to the drug, and then the Ab-(linker portion)^(a) is coupled to drug-(linker portion)^(b) to form the ADC of Formula I. In some such embodiments, the antibody comprises more than one (linker portion)^(a) substituents, such that more than one drug is coupled to the antibody in the ADC of Formula I.

The compounds of the invention expressly contemplate, but are not limited to, ADC prepared with the following linker reagents: bis-maleimido-trioxyethylene glycol (BMPEO), N-(β-maleimidopropyloxy)-N-hydroxy succinimide ester (BMPS), N-(ε-maleimidocaproyloxy) succinimide ester (EMCS), N-[γ-maleimidobutyryloxy]succinimide ester (GMBS), 1,6-hexane-bis-vinylsulfone (HBVS), succinimidyl 4-(N-maleimidomethyl)cyclohexane-1-carboxy-(6-amidocaproate) (LC-SMCC), m-maleimidobenzoyl-N-hydroxysuccinimide ester (MBS), 4-(4-N-Maleimidophenyl)butyric acid hydrazide (MPBH), succinimidyl 3-(bromoacetamido)propionate (SBAP), succinimidyl iodoacetate (SIA), succinimidyl(4-iodoacetyl)aminobenzoate (SIAB), N-succinimidyl-3-(2-pyridyldithio) propionate (SPDP), N-succinimidyl-4-(2-pyridylthio)pentanoate (SPP), succinimidyl 4-(N-maleimidomethyl)cyclohexane-1-carboxylate (SMCC), succinimidyl 4-(p-maleimidophenyl)butyrate (SMPB), succinimidyl 6-[(beta-maleimidopropionamido)hexanoate] (SMPH), iminothiolane (IT), sulfo-EMCS, sulfo-GMBS, sulfo-KMUS, sulfo-MBS, sulfo-SIAB, sulfo-SMCC, and sulfo-SMPB, and succinimidyl-(4-vinylsulfone)benzoate (SVSB), and including bis-maleimide reagents: dithiobismaleimidoethane (DTME), 1,4-Bismaleimidobutane (BMB), 1,4Bismaleimidyl-2,3-dihydroxybutane (BMDB), bismaleimidohexane (BMH), bismaleimidoethane (BMOE), BM(PEG)₂ (shown below), and BM(PEG)₃ (shown below); bifunctional derivatives of imidoesters (such as dimethyl adipimidate HCl), active esters (such as disuccinimidyl suberate), aldehydes (such as glutaraldehyde), bis-azido compounds (such as bis(p-azidobenzoyl) hexanediamine), bis-diazonium derivatives (such as bis-(p-diazoniumbenzoyl)-ethylenediamine), diisocyanates (such as toluene 2,6-diisocyanate), and bis-active fluorine compounds (such as 1,5-difluoro-2,4-dinitrobenzene). In some embodiments, bis-maleimide reagents allow the attachment of the thiol group of a cysteine in the antibody to a thiol-containing drug moiety, linker, or linker-drug intermediate. Other functional groups that are reactive with thiol groups include, but are not limited to, iodoacetamide, bromoacetamide, vinyl pyridine, disulfide, pyridyl disulfide, isocyanate, and isothiocyanate.

Certain useful linker reagents can be obtained from various commercial sources, such as Pierce Biotechnology, Inc. (Rockford, Ill.), Molecular Biosciences Inc. (Boulder, Colo.), or synthesized in accordance with procedures described in the art; for example, in Toki et al (2002) J. Org. Chem. 67:1866-1872; Dubowchik, et al. (1997) Tetrahedron Letters, 38:5257-60; Walker, M. A. (1995) J. Org. Chem. 60:5352-5355; Frisch et al (1996) Bioconjugate Chem. 7:180-186; U.S. Pat. No. 6,214,345; WO 02/088172; US 2003130189; US2003096743; WO 03/026577; WO 03/043583; and WO 04/032828.

Carbon-14-labeled 1-isothiocyanatobenzyl-3-methyldiethylene triaminepentaacetic acid (MX-DTPA) is an exemplary chelating agent for conjugation of radionucleotide to the antibody. See, e.g., WO94/11026.

b) Exemplary Drug Moieties

In some embodiments, an ADC comprises a pyrrolobenzodiazepine (PBD). In some embodiments, PBD dimers recognize and bind to specific DNA sequences. The natural product anthramycin, a PBD, was first reported in 1965 (Leimgruber, et al., (1965) J. Am. Chem. Soc., 87:5793-5795; Leimgruber, et al., (1965) J. Am. Chem. Soc., 87:5791-5793). Since then, a number of PBDs, both naturally-occurring and analogues, have been reported (Thurston, et al., (1994) Chem. Rev. 1994, 433-465 including dimers of the tricyclic PBD scaffold (U.S. Pat. No. 6,884,799; U.S. Pat. No. 7,049,311; U.S. Pat. No. 7,067,511; U.S. Pat. No. 7,265,105; U.S. Pat. No. 7,511,032; U.S. Pat. No. 7,528,126; U.S. Pat. No. 7,557,099). Without intending to be bound by any particular theory, it is believed that the dimer structure imparts the appropriate three-dimensional shape for isohelicity with the minor groove of B-form DNA, leading to a snug fit at the binding site (Kohn, In Antibiotics III. Springer-Verlag, New York, pp. 3-11 (1975); Hurley and Needham-VanDevanter, (1986) Acc. Chem. Res., 19:230-237). Dimeric PBD compounds bearing C2 aryl substituents have been shown to be useful as cytotoxic agents (Hartley et al (2010) Cancer Res. 70(17):6849-6858; Antonow (2010) J. Med. Chem. 53(7):2927-2941; Howard et al (2009) Bioorganic and Med. Chem. Letters 19(22):6463-6466).

In some embodiments, PBD compounds can be employed as prodrugs by protecting them at the N10 position with a nitrogen protecting group which is removable in vivo (WO 00/12507; WO 2005/023814).

PBD dimers have been conjugated to antibodies and the resulting ADC shown to have anti-cancer properties (US 2010/0203007). Nonlimiting exemplary linkage sites on the PBD dimer include the five-membered pyrrolo ring, the tether between the PBD units, and the N10-C11 imine group (WO 2009/016516; US 2009/304710; US 2010/047257; US 2009/036431; US 2011/0256157; WO 2011/130598).

Nonlimiting exemplary PBD dimer components of ADCs are center-linked pyrrolobenzodiazepines of Formula A:

wherein:

R² is

where R^(36a) and R^(36b) are independently selected from H, F, C₁₋₄ saturated alkyl, C₂₋₃ alkenyl, which alkyl and alkenyl groups are optionally substituted by a group selected from C₁₋₄ alkyl amido and C₁₋₄ alkyl ester; or, when one of R^(36a) and R^(36b) is H, the other is selected from nitrile and a C₁₋₄ alkyl ester;

R⁶ and R⁹ are independently selected from H, R, OH, OR, SH, SR, NH₂, NHR, NRR′, NO₂, Me₃Sn and halo;

R⁷ is independently selected from H, R, OH, OR, SH, SR, NH₂, NHR, NRR′, NO₂, Me₃Sn and halo;

Y has the formula:

G comprises a reactive group for connecting to an antibody or G is a linker connected to an antibody;

n is an integer selected in the range of 0 to 48;

R^(A4) is a C₁₋₆ alkylene group;

either

-   -   (a) R¹⁰ is H, and R¹¹ is OH, OR^(A), where R^(A) is C₁₋₄ alkyl;         or     -   (b) R¹⁰ and R¹¹ form a nitrogen-carbon double bond between the         nitrogen and carbon atoms to which they are bound; or     -   (c) R¹⁰ is H and R¹¹ is OSO_(z)M, where z is 2 or 3 and M is a         monovalent pharmaceutically acceptable cation;

R and R′ are each independently selected from optionally substituted C₁₋₁₂ alkyl, C₃₋₂₀ heterocyclyl and C₅₋₂₀ aryl groups, and optionally in relation to the group NRR′, R and R′ together with the nitrogen atom to which they are attached form an optionally substituted 4-, 5-, 6- or 7-membered heterocyclic ring;

wherein R¹⁶, R¹⁷, R¹⁹, R²⁰, R²¹ and R²² are as defined for R⁶, R⁷, R⁹, R¹⁰, R¹¹ and R² respectively;

wherein Z is CH or N;

wherein T and T′ are independently selected from a single bond or a C₁₋₉ alkylene, which chain may be interrupted by one or more heteroatoms e.g. O, S, N(H), NMe, provided that the number of atoms in the shortest chain of atoms between X and X′ is 3 to 12 atoms; and

X and X′ are independently selected from O, S and N(H).

In some embodiments, R⁹ and R¹⁹ are H.

In some embodiments, R⁶ and R¹⁶ are H.

In some embodiments, R⁷ are R¹⁷ are both OR^(7A), where R^(7A) is optionally substituted C₁₋₄ alkyl. In some embodiments, R^(7A) is Me. In some embodiments, R^(7A) is is Ch₂Ph, where Ph is a phenyl group.

In some embodiments, X is O.

In some embodiments, T is selected from a single bond, C₁, and a C₂ alkylene group. In some embodiments, T is a C₁ alkylene group.

In some embodiments, R^(36a) and R^(36b) are both H. In some embodiments, R^(36a) and R^(36b) are both methyl. In some embodiments, one of R^(36a) and R^(36b) is H, and the other is selected from C₁₋₄ saturated alkyl, C₂₋₃ alkenyl, which alkyl and alkenyl groups are optionally substituted. In some embodiments, the group of R^(36a) and R^(36b) which is not H is selected from methyl and ethyl.

In some embodiments, R¹⁰ is H and R¹¹ is OH. In some embodiments, R¹⁰ and R¹¹ form a nitrogen-carbon double bond between the nitrogen and carbon atoms to which they are bound.

In any of the embodiments described herein, R¹⁶, R¹⁷, R¹⁹, R²⁰, R²¹, R²², X′ and T′ may be the same as R⁶, R⁷, R⁹, R¹⁰, R¹¹, R², X and T respectively.

In some embodiments, G comprises a group selected from (i) maleimide groups (ii) activated disulfides, (iii) active esters such as NHS (N-hydroxysuccinimide) esters, HOBt (N-hydroxybenzotriazole) esters, haloformates, and acid halides; (iv) alkyl and benzyl halides such as haloacetamides; and (v) aldehydes, ketones, carboxyl comprises a maleimide group, an activated disulfide, or an electrophilic functional group. In some embodiments, G is a linker connected to an antibody, wherein the linker comprises a moiety derived from an electrophilic functional group selected from (i) maleimide groups (ii) activated disulfides, (iii) active esters such as NHS (N-hydroxysuccinimide) esters, HOBt (N-hydroxybenzotriazole) esters, haloformates, and acid halides; (iv) alkyl and benzyl halides such as haloacetamides; and (v) aldehydes, ketones, carboxyl. In some embodiments, G is:

wherein the wavy line indicates attachment to the remainder of (A1). In some embodiments, G is:

wherein the wavy line indicates attachment to the remainder of (A1) and Ab is an antibody.

In some embodiments, an ADC comprises a center-linked PBD comprising the structure:

wherein Y is defined as above.

A non-limiting exemplary ADC comprising a center-linked PBD dimer may be made by conjugating a center-linked PBD drug linker intermediate (shown below) to an antibody:

to produce a center-linked PBD antibody-drug conjugate:

Another center-linked PBD drug linker intermediate is:

which is conjugated to an antibody to form an ADC:

PBD dimers and ADCs comprising PBD dimers may be prepared according to methods known in the art. See, e.g., WO 2009/016516; US 2009/304710; US 2010/047257; US 2009/036431; US 2011/0256157; WO 2011/130598; WO 2013/055987; WO 2014/159981; WO 2014/140862.

c) Drug Loading

Drug loading is represented by p, the average number of drug moieties per antibody in a molecule of Formula I. Drug loading may range from 1 to 20 drug moieties (D) per antibody. ADCs of Formula I include collections of antibodies conjugated with a range of drug moieties, from 1 to 20. The average number of drug moieties per antibody in preparations of ADC from conjugation reactions may be characterized by conventional means such as mass spectroscopy, ELISA assay, and HPLC. The quantitative distribution of ADC in terms of p may also be determined. In some instances, separation, purification, and characterization of homogeneous ADC where p is a certain value from ADC with other drug loadings may be achieved by means such as reverse phase HPLC or electrophoresis.

For some antibody-drug conjugates, p may be limited by the number of attachment sites on the antibody. For example, where the attachment is a cysteine thiol, as in certain exemplary embodiments above, an antibody may have only one or several cysteine thiol groups, or may have only one or several sufficiently reactive thiol groups through which a linker may be attached. In certain embodiments, higher drug loading, e.g. p>5, may cause aggregation, insolubility, toxicity, or loss of cellular permeability of certain antibody-drug conjugates. In certain embodiments, the average drug loading for an ADC ranges from 1 to about 8; from about 2 to about 6; or from about 3 to about 5. Indeed, it has been shown that for certain ADCs, the optimal ratio of drug moieties per antibody may be less than 8, and may be about 2 to about 5 (U.S. Pat. No. 7,498,298).

In certain embodiments, fewer than the theoretical maximum of drug moieties are conjugated to an antibody during a conjugation reaction. An antibody may contain, for example, lysine residues that do not react with the drug-linker intermediate or linker reagent, as discussed below. Generally, antibodies do not contain many free and reactive cysteine thiol groups which may be linked to a drug moiety; indeed most cysteine thiol residues in antibodies exist as disulfide bridges. In certain embodiments, an antibody may be reduced with a reducing agent such as dithiothreitol (DTT) or tricarbonylethylphosphine (TCEP), under partial or total reducing conditions, to generate reactive cysteine thiol groups. In certain embodiments, an antibody is subjected to denaturing conditions to reveal reactive nucleophilic groups such as lysine or cysteine.

The loading (drug/antibody ratio) of an ADC may be controlled in different ways, and for example, by: (i) limiting the molar excess of drug-linker intermediate or linker reagent relative to antibody, (ii) limiting the conjugation reaction time or temperature, and (iii) partial or limiting reductive conditions for cysteine thiol modification.

It is to be understood that where more than one nucleophilic group reacts with a drug-linker intermediate or linker reagent, then the resulting product is a mixture of ADC compounds with a distribution of one or more drug moieties attached to an antibody. The average number of drugs per antibody may be calculated from the mixture by a dual ELISA antibody assay, which is specific for antibody and specific for the drug. Individual ADC molecules may be identified in the mixture by mass spectroscopy and separated by HPLC, e.g. hydrophobic interaction chromatography (see, e.g., McDonagh et al (2006) Prot. Engr. Design & Selection 19(7):299-307; Hamblett et al (2004) Clin. Cancer Res. 10:7063-7070; Hamblett, K. J., et al. “Effect of drug loading on the pharmacology, pharmacokinetics, and toxicity of an anti-CD30 antibody-drug conjugate,” Abstract No. 624, American Association for Cancer Research, 2004 Annual Meeting, Mar. 27-31, 2004, Proceedings of the AACR, Volume 45, March 2004; Alley, S. C., et al. “Controlling the location of drug attachment in antibody-drug conjugates,” Abstract No. 627, American Association for Cancer Research, 2004 Annual Meeting, Mar. 27-31, 2004, Proceedings of the AACR, Volume 45, March 2004). In certain embodiments, a homogeneous ADC with a single loading value may be isolated from the conjugation mixture by electrophoresis or chromatography.

d) Certain Methods of Preparing Immunoconjugates

An ADC of Formula I may be prepared by several routes employing organic chemistry reactions, conditions, and reagents known to those skilled in the art, including: (1) reaction of a nucleophilic group of an antibody with a bivalent linker reagent to form Ab-L via a covalent bond, followed by reaction with a drug moiety D; and (2) reaction of a nucleophilic group of a drug moiety with a bivalent linker reagent, to form D-L, via a covalent bond, followed by reaction with a nucleophilic group of an antibody. Exemplary methods for preparing an ADC of Formula I via the latter route are described in U.S. Pat. No. 7,498,298, which is expressly incorporated herein by reference.

Nucleophilic groups on antibodies include, but are not limited to: (i)N-terminal amine groups, (ii) side chain amine groups, e.g. lysine, (iii) side chain thiol groups, e.g. cysteine, and (iv) sugar hydroxyl or amino groups where the antibody is glycosylated. Amine, thiol, and hydroxyl groups are nucleophilic and capable of reacting to form covalent bonds with electrophilic groups on linker moieties and linker reagents including: (i) active esters such as NHS esters, HOBt esters, haloformates, and acid halides; (ii) alkyl and benzyl halides such as haloacetamides; and (iii) aldehydes, ketones, carboxyl, and maleimide groups. Certain antibodies have reducible interchain disulfides, i.e. cysteine bridges. Antibodies may be made reactive for conjugation with linker reagents by treatment with a reducing agent such as DTT (dithiothreitol) or tricarbonylethylphosphine (TCEP), such that the antibody is fully or partially reduced. Each cysteine bridge will thus form, theoretically, two reactive thiol nucleophiles. Additional nucleophilic groups can be introduced into antibodies through modification of lysine residues, e.g., by reacting lysine residues with 2-iminothiolane (Traut's reagent), resulting in conversion of an amine into a thiol. Reactive thiol groups may also be introduced into an antibody by introducing one, two, three, four, or more cysteine residues (e.g., by preparing variant antibodies comprising one or more non-native cysteine amino acid residues).

Antibody-drug conjugates of the invention may also be produced by reaction between an electrophilic group on an antibody, such as an aldehyde or ketone carbonyl group, with a nucleophilic group on a linker reagent or drug. Useful nucleophilic groups on a linker reagent include, but are not limited to, hydrazide, oxime, amino, hydrazine, thiosemicarbazone, hydrazine carboxylate, and arylhydrazide. In one embodiment, an antibody is modified to introduce electrophilic moieties that are capable of reacting with nucleophilic substituents on the linker reagent or drug. In another embodiment, the sugars of glycosylated antibodies may be oxidized, e.g. with periodate oxidizing reagents, to form aldehyde or ketone groups which may react with the amine group of linker reagents or drug moieties. The resulting imine Schiff base groups may form a stable linkage, or may be reduced, e.g. by borohydride reagents to form stable amine linkages. In one embodiment, reaction of the carbohydrate portion of a glycosylated antibody with either galactose oxidase or sodium meta-periodate may yield carbonyl (aldehyde and ketone) groups in the antibody that can react with appropriate groups on the drug (Hermanson, Bioconjugate Techniques). In another embodiment, antibodies containing N-terminal serine or threonine residues can react with sodium meta-periodate, resulting in production of an aldehyde in place of the first amino acid (Geoghegan & Stroh, (1992) Bioconjugate Chem. 3:138-146; U.S. Pat. No. 5,362,852). Such an aldehyde can be reacted with a drug moiety or linker nucleophile.

Exemplary nucleophilic groups on a drug moiety include, but are not limited to: amine, thiol, hydroxyl, hydrazide, oxime, hydrazine, thiosemicarbazone, hydrazine carboxylate, and arylhydrazide groups capable of reacting to form covalent bonds with electrophilic groups on linker moieties and linker reagents including: (i) active esters such as NHS esters, HOBt esters, haloformates, and acid halides; (ii) alkyl and benzyl halides such as haloacetamides; (iii) aldehydes, ketones, carboxyl, and maleimide groups.

Nonlimiting exemplary cross-linker reagents that may be used to prepare ADC are described herein in the section titled “Exemplary Linkers.” Methods of using such cross-linker reagents to link two moieties, including a proteinaceous moiety and a chemical moiety, are known in the art. In some embodiments, a fusion protein comprising an antibody and a cytotoxic agent may be made, e.g., by recombinant techniques or peptide synthesis. A recombinant DNA molecule may comprise regions encoding the antibody and cytotoxic portions of the conjugate either adjacent to one another or separated by a region encoding a linker peptide which does not destroy the desired properties of the conjugate.

In yet another embodiment, an antibody may be conjugated to a “receptor” (such as streptavidin) for utilization in tumor pre-targeting wherein the antibody-receptor conjugate is administered to the patient, followed by removal of unbound conjugate from the circulation using a clearing agent and then administration of a “ligand” (e.g., avidin) which is conjugated to a cytotoxic agent (e.g., a drug or radionucleotide).

E. Trastuzumab-MCC-DM1 and Pertuzumab

Trastuzumab-MCC-DM1 (T-DM1)

The present invention includes therapeutic treatments with trastuzumab-MCC-DM1 (T-DM1, also referred to as trastuzumab emtansine), an antibody-drug conjugate (CAS Reg. No. 139504-50-0), which has the structure:

where Tr is trastuzumab linked through linker moiety MCC to the maytansinoid drug moiety DM1 (U.S. Pat. No. 5,208,020; U.S. Pat. No. 6,441,163). The drug to antibody ratio or drug loading is represented by p in the above structure of trastuzumab-MCC-DM1, and ranges in integer values from 1 to about 8. Trastuzumab-MCC-DM1 includes all mixtures of variously loaded and attached antibody-drug conjugates where 1, 2, 3, 4, 5, 6, 7, and 8 drug moieties are covalently attached to the antibody trastuzumab (U.S. Pat. No. 7,097,840; U.S. Pat. No. 8,337,856; US 2005/0276812; US 2005/0166993).

Trastuzumab can be produced by a mammalian cell (Chinese Hamster Ovary, CHO) suspension culture. The HER2 (or c-erbB2) proto-oncogene encodes a transmembrane receptor protein of 185 kDa, which is structurally related to the epidermal growth factor receptor. Trastuzumab is an antibody that has antigen binding residues of, or derived from, the murine 4D5 antibody (ATCC CRL 10463, deposited with American Type Culture Collection, 12301 Parklawn Drive, Rockville, Md. 20852 under the Budapest Treaty on May 24, 1990). Exemplary humanized 4D5 antibodies include huMAb4D5-1, huMAb4D5-2, huMAb4D5-3, huMAb4D5-4, huMAb4D5-5, huMAb4D5-6, huMAb4D5-7 and huMAb4D5-8 (trastuzumab, HERCEPTIN®) as in U.S. Pat. No. 5,821,337. In some embodiments, the antibody portion of T-DM1 comprises the light and heavy chain amino acid sequences shown in SEQ ID NO: 30 and SEQ ID NO. 29, respectively.

Trastuzumab-MCC-DM1 may be prepared according to Example 1 of U.S. Application Publication No. 20110165155, for example.

As a general proposition, the initial pharmaceutically effective amount of trastuzumab-MCC-DM1 administered per dose will be in the range of about 0.3 to 15 mg/kg/day of patient body weight.

A commercial T-DM1 formulation (KADCYLA®, ado-trastuzumab emtansine) is a sterile, white to off-white preservative free lyophilized powder in single-use vials. Each vial contains 100 mg or 160 mg ado-trastuzumab emtansine. Following reconstitution, each single-use vial contains ado-trastuzumab emtansine (20 mg/mL), polysorbate 20 [0.02% (w/v)], sodium succinate (10 mM), and sucrose [6% (w/v)] with a pH of 5.0 and density of 1.026 g/mL. The resulting solution containing 20 mg/mL ado-trastuzumab emtansine is administered by intravenous infusion following dilution. In some embodiments, ado-trastuzumab emtansine is administered at a dose of 3.6 mg/kg every three weeks. In some embodiments, ado-trastuzumab emtansine is administered at a dose of 2.4 mg/kg every week.

Pertuzumab Compositions

The pertuzumab composition comprises a mixture of a main species pertuzumab antibody, as hereinabove defined, and one or more variants thereof. The preferred embodiment herein of a pertuzumab main species antibody is one comprising a light chain amino acid sequence of SEQ ID NO: 32, and a heavy chain amino acid sequence of SEQ ID NO: 31 (including deamidated and/or oxidized variants of those sequences). In some embodiments, the composition comprises a mixture of the main species pertuzumab antibody and an amino acid sequence variant thereof comprising an amino-terminal leader extension, e.g., comprising a light chain amino acid sequence of SEQ ID NO: 34, and a heavy chain amino acid sequence of SEQ ID NO: 33. Preferably, the amino-terminal leader extension is on a light chain of the antibody variant (e.g. on one or two light chains of the antibody variant). The main species HER2 antibody or the antibody variant may be an full length antibody or antibody fragment (e.g. Fab of F(ab′)2 fragments), but preferably both are full length antibodies. The antibody variant herein may comprise an amino-terminal leader extension on any one or more of the heavy or light chains thereof. Preferably, the amino-terminal leader extension is on one or two light chains of the antibody. The amino-terminal leader extension preferably comprises or consists of VHS—. Presence of the amino-terminal leader extension in the composition can be detected by various analytical techniques including, but not limited to, N-terminal sequence analysis, assay for charge heterogeneity (for instance, cation exchange chromatography or capillary zone electrophoresis), mass spectrometry, etc. The amount of the antibody variant in the composition generally ranges from an amount that constitutes the detection limit of any assay (preferably N-terminal sequence analysis) used to detect the variant to an amount less than the amount of the main species antibody. Generally, about 20% or less (e.g. from about 1% to about 15%, for instance from 5% to about 15%) of the antibody molecules in the composition comprise an amino-terminal leader extension. Such percentage amounts are preferably determined using quantitative N-terminal sequence analysis or cation exchange analysis (preferably using a high-resolution, weak cation-exchange column, such as a PROPAC WCX-10™ cation exchange column). Aside from the amino-terminal leader extension variant, further amino acid sequence alterations of the main species antibody and/or variant are contemplated, including but not limited to an antibody comprising a C-terminal lysine residue on one or both heavy chains thereof, a deamidated antibody variant, etc.

Moreover, the main species antibody or variant may further comprise glycosylation variations, non-limiting examples of which include antibody comprising a G1 or G2 oligosaccharide structure attached to the Fc region thereof, antibody comprising a carbohydrate moiety attached to a light chain thereof (e.g. one or two carbohydrate moieties, such as glucose or galactose, attached to one or two light chains of the antibody, for instance attached to one or more lysine residues), antibody comprising one or two non-glycosylated heavy chains, or antibody comprising a sialidated oligosaccharide attached to one or two heavy chains thereof etc.

The composition may be recovered from a genetically engineered cell line, e.g. a Chinese Hamster Ovary (CHO) cell line expressing the HER2 antibody, or may be prepared by peptide synthesis.

For more information regarding exemplary pertuzumab compositions, see U.S. Pat. Nos. 7,560,111 and 7,879,325 as well as US 2009/0202546A1.

A commercial formulation of pertuzumab (PERJETA®) contains pertuzumab 420 mg/14 mL (30 mg/mL) in the form of a preservative-free solution for IV infusion. In some embodiments, pertuzumab therapy comprises administration of an initial loading dose of 840 mg, following by administration of a flat maintenance dose of 420 mg every three weeks.

F. Methods and Compositions for Diagnostics and Detection

In certain embodiments, any of the anti-HER2 antibodies provided herein is useful for detecting the presence of HER2 in a biological sample. The term “detecting” as used herein encompasses quantitative or qualitative detection. A “biological sample” comprises, e.g., a cell or tissue (e.g., biopsy material, including cancerous or potentially cancerous breast tissue).

In one embodiment, an anti-HER2 antibody for use in a method of diagnosis or detection is provided. In a further aspect, a method of detecting the presence of HER2 in a biological sample is provided. In certain embodiments, the method comprises contacting the biological sample with an anti-HER2 antibody as described herein under conditions permissive for binding of the anti-HER2 antibody to HER2, and detecting whether a complex is formed between the anti-HER2 antibody and HER2 in the biological sample. Such method may be an in vitro or in vivo method. In one embodiment, an anti-HER2 antibody is used to select subjects eligible for therapy with an anti-HER2 antibody, e.g. where HER2 is a biomarker for selection of patients. In a further embodiment, the biological sample is a cell or tissue.

In a further embodiment, an anti-HER2 antibody is used in vivo to detect, e.g., by in vivo imaging, a HER2-positive cancer in a subject, e.g., for the purposes of diagnosing, prognosing, or staging cancer, determining the appropriate course of therapy, or monitoring response of a cancer to therapy. One method known in the art for in vivo detection is immuno-positron emission tomography (immuno-PET), as described, e.g., in van Dongen et al., The Oncologist 12:1379-1389 (2007) and Verel et al., J. Nucl. Med. 44:1271-1281 (2003). In such embodiments, a method is provided for detecting a HER2-positive cancer in a subject, the method comprising administering a labeled anti-HER2 antibody to a subject having or suspected of having a HER2-positive cancer, and detecting the labeled anti-HER2 antibody in the subject, wherein detection of the labeled anti-HER2 antibody indicates a HER2-positive cancer in the subject. In certain of such embodiments, the labeled anti-HER2 antibody comprises an anti-HER2 antibody conjugated to a positron emitter, such as ⁶⁸Ga, ¹⁸F, ⁶⁴Cu, ⁸⁶Y, ⁷⁶Br, ⁸⁹Zr, and ¹²⁴I. In a particular embodiment, the positron emitter is ⁸⁹Zr.

In further embodiments, a method of diagnosis or detection comprises contacting a first anti-HER2 antibody immobilized to a substrate with a biological sample to be tested for the presence of HER2, exposing the substrate to a second anti-HER2 antibody, and detecting whether the second anti-HER2 is bound to a complex between the first anti-HER2 antibody and HER2 in the biological sample. A substrate may be any supportive medium, e.g., glass, metal, ceramic, polymeric beads, slides, chips, and other substrates. In certain embodiments, a biological sample comprises a cell or tissue. In certain embodiments, the first or second anti-HER2 antibody is any of the antibodies described herein.

Exemplary disorders that may be diagnosed or detected according to any of the above embodiments include HER2-positive cancers, such as HER2-positive breast cancer and HER2-positive gastric cancer. In some embodiments, HER2-positive cancer has an immunohistochemistry (IHC) score of 2+ or 3+ and/or an in situ hybridization (ISH) amplification ratio ≧2.0.

In certain embodiments, labeled anti-HER2 antibodies are provided. Labels include, but are not limited to, labels or moieties that are detected directly (such as fluorescent, chromophoric, electron-dense, chemiluminescent, and radioactive labels), as well as moieties, such as enzymes or ligands, that are detected indirectly, e.g., through an enzymatic reaction or molecular interaction. Exemplary labels include, but are not limited to, the radioisotopes ³²P, ¹⁴C, ¹²⁵I, ³H, and ¹³¹I, fluorophores such as rare earth chelates or fluorescein and its derivatives, rhodamine and its derivatives, dansyl, umbelliferone, luceriferases, e.g., firefly luciferase and bacterial luciferase (U.S. Pat. No. 4,737,456), luciferin, 2,3-dihydrophthalazinediones, horseradish peroxidase (HRP), alkaline phosphatase, β-galactosidase, glucoamylase, lysozyme, saccharide oxidases, e.g., glucose oxidase, galactose oxidase, and glucose-6-phosphate dehydrogenase, heterocyclic oxidases such as uricase and xanthine oxidase, coupled with an enzyme that employs hydrogen peroxide to oxidize a dye precursor such as HRP, lactoperoxidase, or microperoxidase, biotin/avidin, spin labels, bacteriophage labels, stable free radicals, and the like. In another embodiment, a label is a positron emitter. Positron emitters include but are not limited to ⁶⁸Ga, ¹⁸F, ⁶⁴Cu, ⁸⁶Y, ⁷⁶Br, ⁸⁹Zr, and ¹²⁴I. In a particular embodiment, a positron emitter is ⁸⁹Zr.

G. Pharmaceutical Formulations

Pharmaceutical formulations of an anti-HER2 antibody or immunoconjugate as described herein are prepared by mixing such antibody or immunoconjugate having the desired degree of purity with one or more optional pharmaceutically acceptable carriers (Remington's Pharmaceutical Sciences 16th edition, Osol, A. Ed. (1980)), in the form of lyophilized formulations or aqueous solutions. Pharmaceutically acceptable carriers are generally nontoxic to recipients at the dosages and concentrations employed, and include, but are not limited to: buffers such as phosphate, citrate, and other organic acids; antioxidants including ascorbic acid and methionine; preservatives (such as octadecyldimethylbenzyl ammonium chloride; hexamethonium chloride; benzalkonium chloride; benzethonium chloride; phenol, butyl or benzyl alcohol; alkyl parabens such as methyl or propyl paraben; catechol; resorcinol; cyclohexanol; 3-pentanol; and m-cresol); low molecular weight (less than about 10 residues) polypeptides; proteins, such as serum albumin, gelatin, or immunoglobulins; hydrophilic polymers such as polyvinylpyrrolidone; amino acids such as glycine, glutamine, asparagine, histidine, arginine, or lysine; monosaccharides, disaccharides, and other carbohydrates including glucose, mannose, or dextrins; chelating agents such as EDTA; sugars such as sucrose, mannitol, trehalose or sorbitol; salt-forming counter-ions such as sodium; metal complexes (e.g. Zn-protein complexes); and/or non-ionic surfactants such as polyethylene glycol (PEG). Exemplary pharmaceutically acceptable carriers herein further include insterstitial drug dispersion agents such as soluble neutral-active hyaluronidase glycoproteins (sHASEGP), for example, human soluble PH-20 hyaluronidase glycoproteins, such as rHuPH₂O (HYLENEX®, Baxter International, Inc.). Certain exemplary sHASEGPs and methods of use, including rHuPH20, are described in US Patent Publication Nos. 2005/0260186 and 2006/0104968. In one aspect, a sHASEGP is combined with one or more additional glycosaminoglycanases such as chondroitinases.

Exemplary lyophilized antibody or immunoconjugate formulations are described in U.S. Pat. No. 6,267,958. Aqueous antibody or immunoconjugate formulations include those described in U.S. Pat. No. 6,171,586 and WO2006/044908, the latter formulations including a histidine-acetate buffer.

The formulation herein may also contain more than one active ingredient as necessary for the particular indication being treated, preferably those with complementary activities that do not adversely affect each other.

Active ingredients may be entrapped in microcapsules prepared, for example, by coacervation techniques or by interfacial polymerization, for example, hydroxymethylcellulose or gelatin-microcapsules and poly-(methylmethacylate) microcapsules, respectively, in colloidal drug delivery systems (for example, liposomes, albumin microspheres, microemulsions, nano-particles and nanocapsules) or in macroemulsions. Such techniques are disclosed in Remington's Pharmaceutical Sciences 16th edition, Osol, A. Ed. (1980).

Sustained-release preparations may be prepared. Suitable examples of sustained-release preparations include semipermeable matrices of solid hydrophobic polymers containing the antibody or immunoconjugate, which matrices are in the form of shaped articles, e.g. films, or microcapsules.

The formulations to be used for in vivo administration are generally sterile. Sterility may be readily accomplished, e.g., by filtration through sterile filtration membranes.

H. Therapeutic Methods and Compositions

Any of the anti-HER2 antibodies or immunoconjugates provided herein may be used in methods, e.g., therapeutic methods.

In one aspect, an anti-HER2 antibody or immunoconjugate provided herein is used in a method of inhibiting proliferation of a HER2-positive cell, the method comprising exposing the cell to the anti-HER2 antibody or immunoconjugate under conditions permissive for binding of the anti-HER2 antibody or immunoconjugate to HER2 on the surface of the cell, thereby inhibiting the proliferation of the cell. In certain embodiments, the method is an in vitro or an in vivo method. In further embodiments, the cell is a breast cancer cell or a gastric cancer cell.

Inhibition of cell proliferation in vitro may be assayed using the CellTiter-Glo™ Luminescent Cell Viability Assay, which is commercially available from Promega (Madison, Wis.). That assay determines the number of viable cells in culture based on quantitation of ATP present, which is an indication of metabolically active cells. See Crouch et al. (1993) J. Immunol. Meth. 160:81-88, U.S. Pat. No. 6,602,677. The assay may be conducted in 96- or 384-well format, making it amenable to automated high-throughput screening (HTS). See Cree et al. (1995) AntiCancer Drugs 6:398-404. The assay procedure involves adding a single reagent (CellTiter-Glo® Reagent) directly to cultured cells. This results in cell lysis and generation of a luminescent signal produced by a luciferase reaction. The luminescent signal is proportional to the amount of ATP present, which is directly proportional to the number of viable cells present in culture. Data can be recorded by luminometer or CCD camera imaging device. The luminescence output is expressed as relative light units (RLU).

In another aspect, an anti-HER2 antibody or immunoconjugate for use as a medicament is provided. In further aspects, an anti-HER2 antibody or immunoconjugate for use in a method of treatment is provided. In certain embodiments, an anti-HER2 antibody or immunoconjugate for use in treating HER2-positive cancer is provided. In certain embodiments, the invention provides an anti-HER2 antibody or immunoconjugate for use in a method of treating an individual having a HER2-positive cancer, the method comprising administering to the individual an effective amount of the anti-HER2 antibody or immunoconjugate. In one such embodiment, the method further comprises administering to the individual an effective amount of at least one additional therapeutic agent, e.g., as described below.

In a further aspect, the invention provides for the use of an anti-HER2 antibody or immunoconjugate in the manufacture or preparation of a medicament. In one embodiment, the medicament is for treatment of HER2-positive cancer. In a further embodiment, the medicament is for use in a method of treating HER2-positive cancer, the method comprising administering to an individual having HER2-positive cancer an effective amount of the medicament. In one such embodiment, the method further comprises administering to the individual an effective amount of at least one additional therapeutic agent, e.g., as described below.

In a further aspect, the invention provides a method for treating HER2-positive cancer. In one embodiment, the method comprises administering to an individual having such HER2-positive cancer an effective amount of an anti-HER2 antibody or immunoconjugate. In one such embodiment, the method further comprises administering to the individual an effective amount of at least one additional therapeutic agent, as described below.

A HER2-positive cancer according to any of the above embodiments may be, e.g., HER2-positive breast cancer or HER2-positive gastric cancer. In some embodiments, HER2-positive cancer has an immunohistochemistry (IHC) score of 2+ or 3+ and/or an in situ hybridization (ISH) amplification ratio ≧2.0.

An “individual,” “patient,” or “subject” according to any of the above embodiments may be a human.

In a further aspect, the invention provides pharmaceutical formulations comprising any of the anti-HER2 antibodies or immunoconjugate provided herein, e.g., for use in any of the above therapeutic methods. In one embodiment, a pharmaceutical formulation comprises any of the anti-HER2 antibodies or immunoconjugates provided herein and a pharmaceutically acceptable carrier. In another embodiment, a pharmaceutical formulation comprises any of the anti-HER2 antibodies or immunoconjugates provided herein and at least one additional therapeutic agent, e.g., as described below.

Antibodies or immunoconjugates of the invention can be used either alone or in combination with other agents in a therapy. For instance, an antibody or immunoconjugate of the invention (e.g., a hu7C2.v.2.2.LA antibody-drug conjugate (hu7C2 ADC)) may be co-administered with at least one additional therapeutic agent. In some embodiments, the additional therapeutic agent is also an antibody or immunoconjugate that binds to HER2. In some embodiments, the additional therapeutic agent is (i) an antibody or immunoconjugate that binds to domain II of HER2, and/or (ii) an antibody or immunoconjugate that binds to domain IV or HER2. In some embodiments, the additional therapeutic agent is (i) an antibody or immunoconjugate that binds to epitope 2C4, and/or (ii) an antibody or immunoconjugate that binds to epitope 4D5.

In some embodiments, a hu7C2.v.2.2.LA antibody-drug conjugate (hu7C2 ADC) is co-administered with one or more additional therapeutic agents selected from trastuzumab (Herceptin®), T-DM1 (Kadcyla®) and pertuzumab (Perjeta®). In some embodiments, an hu7C2 ADC is co-administered with trastuzumab. In some embodiments, a hu7C2 ADC is co-administered with T-DM1. In some embodiments, a hu7C2 ADC is co-administered with pertuzumab. In some embodiments, a hu7C2 ADC is co-administered with trastuzumab and pertuzumab. In some embodiments, a hu7C2 ADC is co-administered with T-DM1 and pertuzumab.

Such combination therapies noted above encompass combined administration (where two or more therapeutic agents are included in the same or separate formulations), and separate administration, in which case, administration of the antibody or immunoconjugate of the invention can occur prior to, simultaneously, and/or following, administration of the additional therapeutic agent and/or adjuvant. Antibodies or immunoconjugates of the invention can also be used in combination with radiation therapy.

An antibody or immunoconjugate of the invention (and any additional therapeutic agent) can be administered by any suitable means, including parenteral, intrapulmonary, and intranasal, and, if desired for local treatment, intralesional administration. Parenteral infusions include intramuscular, intravenous, intraarterial, intraperitoneal, or subcutaneous administration. Dosing can be by any suitable route, e.g. by injections, such as intravenous or subcutaneous injections, depending in part on whether the administration is brief or chronic. Various dosing schedules including but not limited to single or multiple administrations over various time-points, bolus administration, and pulse infusion are contemplated herein.

Antibodies or immunoconjugates of the invention would be formulated, dosed, and administered in a fashion consistent with good medical practice. Factors for consideration in this context include the particular disorder being treated, the particular mammal being treated, the clinical condition of the individual patient, the cause of the disorder, the site of delivery of the agent, the method of administration, the scheduling of administration, and other factors known to medical practitioners. The antibody or immunoconjugate need not be, but is optionally formulated with one or more agents currently used to prevent or treat the disorder in question. The effective amount of such other agents depends on the amount of antibody or immunoconjugate present in the formulation, the type of disorder or treatment, and other factors discussed above. These are generally used in the same dosages and with administration routes as described herein, or about from 1 to 99% of the dosages described herein, or in any dosage and by any route that is empirically/clinically determined to be appropriate.

For the prevention or treatment of disease, the appropriate dosage of an antibody or immunoconjugate of the invention (when used alone or in combination with one or more other additional therapeutic agents) will depend on the type of disease to be treated, the type of antibody or immunoconjugate, the severity and course of the disease, whether the antibody or immunoconjugate is administered for preventive or therapeutic purposes, previous therapy, the patient's clinical history and response to the antibody or immunoconjugate, and the discretion of the attending physician. The antibody or immunoconjugate is suitably administered to the patient at one time or over a series of treatments. Depending on the type and severity of the disease, about 1 mg/kg to 15 mg/kg (e.g. 0.1 mg/kg-10 mg/kg) of antibody or immunoconjugate can be an initial candidate dosage for administration to the patient, whether, for example, by one or more separate administrations, or by continuous infusion. One typical daily dosage might range from about 1 mg/kg to 100 mg/kg or more, depending on the factors mentioned above. For repeated administrations over several days or longer, depending on the condition, the treatment would generally be sustained until a desired suppression of disease symptoms occurs. One exemplary dosage of the antibody or immunoconjugate would be in the range from about 0.05 mg/kg to about 10 mg/kg. Thus, one or more doses of about 0.5 mg/kg, 2.0 mg/kg, 4.0 mg/kg or 10 mg/kg (or any combination thereof) may be administered to the patient. Such doses may be administered intermittently, e.g. every week or every three weeks (e.g. such that the patient receives from about two to about twenty, or e.g. about six doses of the antibody). An initial higher loading dose, followed by one or more lower doses may be administered. However, other dosage regimens may be useful. The progress of this therapy is easily monitored by conventional techniques and assays.

It is understood that any of the above formulations or therapeutic methods may be carried out using both an immunoconjugate of the invention and an anti-HER2 antibody.

I. Articles of Manufacture

Articles of manufacture, or “kits”, containing a hu7C2.v.2.2.LA antibody-drug conjugate (hu7C2 ADC) and trastuzumab-MCC-DM1 and/or pertuzumab useful for the treatment methods herein are provided. In some embodiments, the kit comprises a container comprising a hu7C2 ADC. In some embodiments, the kit further comprises a container comprising trastuzumab-MCC-DM1. In some embodiments, the kit further comprises container comprising pertuzumab. In some embodiments, a kit further comprises a container comprising trastuzumab-MCC-DM1 and a container comprising pertuzumab. In some embodiments, the kit comprises two or more of hu7C2 ADC, trastuzumab-MCC-DM1, and pertuzumab in the same container. The kit may further comprise a label or package insert, on or associated with the container. The term“package insert” is used to refer to instructions customarily included in commercial packages of therapeutic products, that contain information about the indications, usage, dosage, administration, contraindications and/or warnings concerning the use of such therapeutic products. Suitable containers include, for example, bottles, vials, syringes, blister pack, etc. The container may be formed from a variety of materials such as glass or plastic. The container may hold hu7C2 ADC and, optionally, trastuzumab-MCC-DM1 and/or pertuzumab or a formulation thereof which is effective for use in a treatment method herein, and may have a sterile access port (for example, the container may be an intravenous solution bag or a vial having a stopper pierceable by a hypodermic injection needle). The label or package insert indicates that the composition is used in a treatment method as described and claimed herein. The article of manufacture may also contain a further container comprising a pharmaceutically acceptable buffer, such as bacteriostatic water for injection (BWFI), phosphate-buffered saline, Ringer's solution and dextrose solution. It may further include other materials desirable from a commercial and user standpoint, including other buffers, diluents, filters, needles, and syringes.

The kit may further comprise directions for the administration of hu7C2 ADC and, optionally, trastuzumab-MCC-DM1 and/or pertuzumab. For example, if the kit comprises a first composition comprising hu7C2 ADC and a second pharmaceutical formulation, the kit may further comprise directions for the simultaneous, sequential or separate administration of the first and second pharmaceutical compositions to a patient in need thereof.

In another embodiment, the kits are suitable for the delivery of solid oral forms of hu7C2 ADC and, optionally, trastuzumab-MCC-DM1 and/or pertuzumab, such as tablets or capsules. Such a kit preferably includes a number of unit dosages. Such kits can include a card having the dosages oriented in the order of their intended use. An example of such a kit is a “blister pack”. Blister packs are well known in the packaging industry and are widely used for packaging pharmaceutical unit dosage forms. If desired, a memory aid can be provided, for example in the form of numbers, letters, or other markings or with a calendar insert, designating the days in the treatment schedule in which the dosages can be administered.

According to one embodiment, a kit may comprise (a) a first container with hu7C2 ADC, and optionally, (b) a second container with trastuzumab-MCC-DM1 contained therein and/or with pertuzumab contained therein. In some embodiments, a kit may comprise (a) a first container with hu7C2 ADC, (b) a second container with trastuzumab-MCC-DM1 contained therein, and (c) a third container with pertuzumab contained therein. In some embodiments, the kit may further comprise a container comprising a pharmaceutically-acceptable buffer, such as bacteriostatic water for injection (BWFI), phosphate-buffered saline, Ringer's solution and dextrose solution. It may further include other materials desirable from a commercial and user standpoint, including other buffers, diluents, filters, needles, and syringes.

Where the kit comprises a composition of hu7C2 ADC and trastuzumab-MCC-DM1 and/or pertuzumab, the kit may comprise a container for containing the separate compositions such as a divided bottle or a divided foil packet, however, the separate compositions may also be contained within a single, undivided container. Typically, the kit comprises directions for the administration of the separate components. The kit form is particularly advantageous when the separate components are preferably administered in different dosage forms (e.g., oral and parenteral), are administered at different dosage intervals, or when titration of the individual components of the combination is desired by the prescribing physician.

One embodiment of an article of manufacture herein comprises an intravenous (IV) bag containing a stable mixture of a hu7C2 ADC and pertuzumab and/or T-DM1 suitable for administration to a cancer patient. Optionally, the mixture is in saline solution; for example comprising about 0.9% NaCl or about 0.45% NaCl. An exemplary IV bag is a polyolefin or polyvinyl chloride infusion bag, e.g. a 250 mL IV bag. According to some embodiments of the invention, the mixture includes about 420 mg or about 840 mg of pertuzumab and from about 100 mg to about 160 mg T-DM1.

Optionally, the mixture in the IV bag is stable for up to 24 hours at 5° C. or 30° C. Stability of the mixture can be evaluated by one or more assays selected from the group consisting of: color, appearance and clarity (CAC), concentration and turbidity analysis, particulate analysis, size exclusion chromatography (SEC), ion-exchange chromatography (IEC), capillary zone electrophoresis (CZE), image capillary isoelectric focusing (iCIEF), and potency assay.

III. Examples

The following are examples of methods and compositions of the invention. It is understood that various other embodiments may be practiced, given the general description provided above.

Example 1: Humanization of Murine Antibody 7C2

Anti-HER2 murine antibody 7C2 binds to an epitope in domain I of HER2. See, e.g., PCT Publication No. WO 98/17797. This epitope is distinct from the epitope bound by trastuzumab, which binds to domain IV of HER2, and the epitope bound by pertuzumab, which binds to domain II of HER2. See FIGS. 3, 16, and 18. By binding domain IV, trastuzumab disrupts ligand-independent HER2-HER3 complexes, thereby inhibiting downstream signaling (e.g. PI3K/AKT). In contrast, pertuzumab binding to domain II prevents ligand-driven HER2 interaction with other HER family members (e.g. HER3, HER1 or HER4), thus also preventing downstream signal transduction. Binding of MAb 7C2 to domain I does not result in interference of trastuzumab or pertuzumab binding to domains IV and II, respectively, thereby offering the potential of combining a MAb 7C2 ADC with trastuzumab, trastuzumab emtansine (T-DM-1), and/or pertuzumab.

Murine antibody 7C2 (7C2.B9, see PCT Publication No. WO 98/17797) was humanized as follows.

A. Materials and Methods

Residue numbers are according to Kabat (Kabat et al., Sequences of proteins of immunological interest, 5th Ed., Public Health Service, National Institutes of Health, Bethesda, Md. (1991)).

Direct Hypervariable Region Grafts onto the Acceptor Human Consensus Framework.

Variants constructed during the humanization of 7C2 were assessed in the form of an IgG. The VL and VH domains from murine 7C2 were aligned with the human VL kappa IV (VL_(KIV)) and human VH subgroup I (VH₁) consensus sequences. Hypervariable regions (HVR) from the murine 7C2 (7C2.B9) antibody were engineered into VL_(KIV) and VH₁ acceptor frameworks to generate CDR-graft variants. From the mu7C2 VL domain, positions 24-34 (L1), 50-56 (L2) and 89-97 (L3) were grafted into VL_(KI). From the mu7C2 VH domain, positions 26-35 (H1), 50-65 (H2) and 95-102 (H3) were grafted into VH₁ (FIGS. 1 and 2). The HVR definitions are defined by their sequence hypervariability (Wu, T. T. & Kabat, E. A. (1970)), their structural location (Chothia, C. & Lesk, A. M. (1987)) and their involvement in antigen-antibody contacts (MacCallum et al. J. Mol. Biol. 262: 732-745 (1996)). To evaluate framework vernier positions that might be important, selected vernier positions were mutated back to the murine sequence. The vernier positions include positions 4 and 49 in VL and positions 37, 67, 69, 71 and 73 in VH. Three different versions of VL sequences and VH sequences were synthesized (Blue Heron, Bothell, Wash.) and subsequently subcloned into mammalian expression vectors. By combining the different versions of LC with HC, a total of nine different hu7C2 graft variants (v1.1, v1.2, v1.3, v2.1, v2.2, v2.3, v3.1, v3.2 and v3.3) were generated.

Affinity Maturation Library.

A monovalent Fab-g3 display phagemid vector with 2 open reading frames under control of a single phoA promoter was used. The first open reading frame consists of the stII signal sequence fused to the VL and CL domains of the acceptor light chain and the second consists of the stII signal sequence fused to the VH and CH1 domains of the acceptor heavy chain followed by the minor phage coat protein P3. The HVR graft variant (7C2.v2.1) was generated by Kunkel mutagenesis using separate oligonucleotides for each hypervariable region, and displayed on phage as a Fab.

To improve affinity, phage libraries containing changes in each hypervariable region were generated. Sequence diversity was introduced separately at each position in the hypervariable regions of 7C2.v2.1 using Kunkel mutagenesis. Positions in the hypervariable region of 7C2.v2.1 were each fully randomized one at a time to all possible 20 amino acids using oligonucleotides encoding NNS. A total of 68 libraries, each consisting of 20 members, were made having a single position located within one of the hypervariable regions of 7C2 fully randomized. Libraries with positions in the same hypervariable region were pooled to generate a total of six libraries.

Generation of Phage Libraries.

Oligonucleotides designed to introduce diversity into each hypervariable region as outlined above were phosphorylated separately in 20 μl reactions containing 660 ng of oligonucleotide, 50 mM Tris pH 7.5, 10 mM MgCl₂, 1 mM ATP, 20 mM DTT, and 5 U polynucleotide kinase for 1 h at 37° C.

To generate the affinity maturation library, 68 individual Kunkel mutagenesis reactions were performed in a 96-well PCR plate. From the phosphorylated oligonucleotides reactions (above), 2 μl was added to 500 ng Kunkel template in 50 mM Tris pH 7.5, 10 mM MgCl₂ in a final volume of 25 μl. The mixture was annealed at 90° C. for 1 min, 50° C. for 3 min and then cooled on ice. The annealed template was then filled in by adding 0.5 μl 10 mM ATP, 0.5 μl 10 mM dNTPs (10 mM each of dATP, dCTP, dGTP and dTTP), 1 μl 100 mM DTT, 1 μl 10×TM buffer (0.5 M Tris pH 7.5, 0.1 M MgCl₂), 80 U T4 ligase, and 4 U T7 polymerase in a total volume of 30 μl for 2 h at room temperature. These filled-in and ligated products were then each transformed into XL1-blue cells. The libraries containing positions in the same CDR region were pooled and recovered in 10 ml SOC media for 1 hour at 37° C. Carbenacillin (50 μg/ml) and M13/KO7 helper phage (MOI 10) were added. The cultures were incubated for another 30 mins at 37° C. and transferred to 500 ml 2YT containing 50 μg/ml carbenacillin and 50 μg/ml kanamycin and grown 20 h at 37° C.

Phage Selections.

Her2 extracellular domain (Her2 ECD) was biotinylated through free amines using NHS-PEG4-Biotin (Pierce). For biotinylation reactions, a 4-fold molar excess of biotin reagent was used in PBS. Reactions were followed by dialysis in PBS.

Phage were harvested from the cell culture supernatant and suspended in PBS containing 1% BSA. The phage libraries were incubated with biotinylated Her2 ECD at room temperature and the phage bound to biotin-Her2 was then captured for 5 min on neutrAvidin (10 μg/ml) that had been immobilized in PBS on MaxiSorp microtiter plates (Nunc) overnight at 4° C. Microtiter wells were washed extensively with PBS containing 0.05% Tween 20 (PBST) and bound phage were eluted by incubating the wells with 20 mM HCl, 500 mM KCl for 30 min. Eluted phage were neutralized with 1 M Tris, pH 7.5 and amplified using XL1-Blue cells and M13/KO7 helper phage and grown overnight at 37° C. in 2YT, 50 μg/ml carbenacillin and 50 μg/ml Kanamycin. The titers of phage eluted from a target containing well were compared to titers of phage recovered from a non-target containing well to assess enrichment. Selection stringency was increased by both decreasing concentration of biotinylated Her2 ECD (from 5 nM to 0.2 nM) during binding and increasing the competition time (from 0 to 60 min at room temperature) with 1 μM of unlabeled Her2 ECD in solution.

Surface Plasmon Resonance Assessment of Variants.

7C2 variants were expressed as IgG by 293 transient transfection. IgG was purified with protein A affinity chromatography. The affinity of each 7C2 IgG variant for Her2 was determined by surface plasmon resonance using a BIAcoreT100. Biacore Series S CMS sensor chips were immobilized with monoclonal mouse anti-human IgG (Fc) antibody (Human antibody capture kit, GE Healthcare). Serial 3-fold dilutions of each 7C2 variant were injected at a flow rate of 30 μl/min. Each sample was analyzed with 3-minute association and 10-minute dissociation. After each injection the chip was regenerated using 3 M MgCl₂. Binding response was corrected by subtracting the RU from a flow cell capturing an irrelevant IgG at similar density. A 1:1 Languir model of simultaneous fitting of k_(on) and k_(off) was used for kinetics analysis.

B. Results and Discussion

Humanization of 7C2.

The human acceptor frameworks used for humanization of 7C2 are based on the human VL kappa IV consensus (VL_(KIV)) and the human VH₁ consensus. The VL and VH domains of murine 7C2 were aligned with the human VL_(KIV) and VH₁ domains; hypervariable regions were identified and grafted into the human acceptor framework to generate 7C2.v1.1. The monovalent affinity of 7C2.v1.1 is decreased 2.5-fold relative to mu7C2.B9 as assessed by SPR (see Table 2).

TABLE 2 Affinity of 7C2 CDR grafted antibodies VL K_(D) (nM) K4 K4.K49 K4.L4.K49 VH VH1 v1.1 v2.1 v3.1 (20 nM) (16 nM) (15 nM) VH1.V71 v1.2 v2.2 v3.2 (13 nM) (11 nM) (10 nM) VH1.L37.A67.L69.V71.K73 v1.3 v2.3 v3.3 (11 nM) (10 nM) (9 nM)

To improve the binding affinity of 7C2.v1.1, positions 4 and 49 in the light chain and positions 37, 67, 69, 71 and 73 in the heavy chain were changed to residues found at these positions in mu7C2.B9. Combinations of these altered light and heavy chains with chains from 7C2.v1.1 were transfected into 293 cells, expressed as IgG and purified, and assessed for binding to Her2 ECD by SPR (see Table 2). Variant 7C2.v3.3, which contains 2 altered positions in light chain and 5 altered positions in heavy chain, had a monovalent affinity comparable to mu7C2.B9 (see Table 4).

Affinity maturation libraries were explored in an effort to recruit further improvements using the framework of 7C2.v2.1, which contains minimal altered vernier position (Y49K) in light chain. For each hypervariable region, all 20 amino acids were introduced separately at individual position using Kunkle mutagenesis (a total of 68 libraries, each containing 20 members, pooled into six affinity maturation libraries). The six affinity maturation libraries were panned for 4 rounds in solution with biotinylated Her2 ECD. Selection stringency was gradually increased by decreasing the concentration of biotin-Her2 ECD (from 5 to 0.2 nM) and increasing the competition time (from 0 to 1 hour at room temperature) with saturated amount of unlabeled Her2 ECD. A two thousand fold of phage enrichment was observed for the H2 library.

A total of 588 clones from the last round were picked for DNA sequence analysis. Individual sequence changes were identified in each HVR (see Table 3). The most abundant clones had changes in VH at position S53 to Met or Leu. The S53M and S53L variants were expressed as IgG and SPR analysis indicate that S53M and S53L have comparable affinity to Her2. The S53L variant was selected since methionine is prone to oxidation during the manufacturing process. A potential iso-aspartic acid forming site in HVR—H2 was eliminated with a S55A mutation (see Table 4).

TABLE 3 Kinetics of affinity-improved variants k_(a) k_(d) K_(D) Variant HVR-H1 HVR-H2 HVR-H3 (1/Ms) (1/s) (nM) v2.1 GYWMN MIHPSDSEIRANQKFRD GTYDGGFEY 2.6E+05 4.1E−03 15.5 (SEQ ID NO: 15) (SEQ ID NO: 8) (SEQ ID NO: 17) v2.1.S53M MIHPMDSEIRANQKFRD 2.7E+05 6.7E−04 2.4 (SEQ ID NO: 20) v2.1.S53L MIHPLDSEIRANQKFRD 2.5E+05 8.5E−04 3.4 (SEQ ID NO: 21) v2.1.E101K GTYDGGFKY 2.2E+05 1.5E−03 6.8 (SEQ ID NO: 22)

TABLE 4 Summary of hu7C2 variant affinities hu7C2 variant K_(D) (nM) mu7C2.B9 8 hu7C2.v2.2 11 hu7C2.v2.2.LA (S53L, S55A); 3 HVR-H2 of SEQ ID NO: 16

An alignment of the human VL_(KIV) and VH₁ domains and the heavy chain and light chain variable regions of mu7C2.B9 (“7C2”) and hu7C2.v2.2.LA (referred to in the following examples as “hu7C2”) is shown in FIGS. 1 and 2.

Example 2: Production of hu7C2 Antibody Drug Conjugates

For larger scale antibody production, antibodies were produced in CHO cells. Vectors coding for heavy chain and light chain were transfected into CHO cells and IgG was purified from cell culture media by protein A affinity chromatography.

A. Synthesis of Center-Linked PBD Linker Drug Intermediate

The center-linked PBD linker drug intermediate (N-(3-(3,5-bis((((S)-7-methoxy-2-methylene-5-oxo-2,3,5,11a-tetrahydro-1H-pyrrolo[2,1-c][1,4]benzodiazepin-8-yl)oxy)methyl)phenyl)prop-2-yn-1-yl)-1-(3-(2,5-dioxo-2,5-dihydro-1H-pyrrol-1-yl)propanamido)-3,6,9,12-tetraoxapentadecan-15-amide; “10”) having the following formula:

was synthesized as follows.

1. (11S,11aS,11′S,11a′S)-di-tert-butyl8,8′-(((5-iodo-1,3-phenylene)bis(methylene))bis(oxy))bis(7-methoxy-2-methylene-5-oxo-11-((tetrahydro-2H-pyran-2-yl)oxy)-2,3,11,11a-tetrahydro-1H-pyrrolo[2,1-c][1,4]benzodiazepine-10(5H)-carboxylate) (2a)

1,3-bis(bromomethyl)-5-iodobenzene (2.00 g, 5.20 mmol) was added to a stirred solution of Boc/THP-protected PBD capping unit 1 (4.75 g, 10.3 mmol), TBAI (190 mg, 0.52 mmol) and K₂CO₃ (1.42 g, 10.3 mmol) in dry DMF (60 mL). The reaction mixture was heated to 60° C. and stirred under an argon atmosphere for 3 hours at which point analysis by LC/MS revealed substantial product formation at retention time 4.15 min (ES+) m/z 1171 ([M+Na]⁺, ˜10% relative intensity). The reaction mixture was allowed to cool to room temperature and the DMF was removed by evaporation in vacuo. The resulting residue was partitioned between water (50 mL) and EtOAc (50 mL) and the aqueous phase was extracted with EtOAc (3×20 mL). The combined organic layers were washed with water (2×20 mL), brine (50 mL), dried (MgSO₄), filtered and evaporated in vacuo to provide the crude product. Purification by flash chromatography (gradient elution: 50:50 v/v EtOAc/hexane to 80:20 v/v EtOAc/hexane) gave the bis-ether 2a as a white foam (5.42 g, 91% yield).

2. (11S,11aS,11′S,11a′S)-di-tert-butyl8,8′-(((5-bromo-1,3-phenylene)bis(methylene))bis(oxy))bis(7-methoxy-2-methylene-5-oxo-11-((tetrahydro-2H-pyran-2-yl)oxy)-2,3,11,11a-tetrahydro-1H-pyrrolo[2,1-c][1,4]benzodiazepine-10(5H)-carboxylate) (2b

1-bromo-3,5-bis(bromomethyl)benzene (1.54 g, 4.53 mmol) was added to a stirred solution of Boc/THP-protected PBD capping unit 1 (4.20 g, 9.06 mmol), TBAI (167 mg, 0.45 mmol) and K₂CO₃ (1.25 g, 9.06 mmol) in dry DMF (52 mL). The reaction mixture was heated to 60° C. and stirred under an argon atmosphere for 5 hours at which point analysis by LC/MS revealed substantial product formation at retention time 4.10 min (ES+) m/z 1101 ([M+H]⁺, ˜70% relative intensity). The reaction mixture was allowed to cool to room temperature and the DMF was removed by evaporation in vacuo. The resulting residue was partitioned between water (60 mL) and EtOAc (60 mL) and the aqueous phase was extracted with EtOAc (3×25 mL). The combined organic layers were washed with water (30 mL), brine (50 mL), dried (MgSO₄), filtered and evaporated in vacuo to provide the crude product. Purification by flash chromatography (gradient elution: 50:50 v/v EtOAc/hexane to 100% EtOAc) gave the bis-ether 2b as a white foam (3.37 g, 68% yield).

3. (115,11aS,11′S,11a′S)-di-tert-butyl8,8′-(((5-chloro-1,3-phenylene)bis(methylene))bis(oxy))bis(7-methoxy-2-methylene-5-oxo-11-((tetrahydro-2H-pyran-2-yl)oxy)-2,3,11,11a-tetrahydro-1H-pyrrolo[2,1-c][1,4]benzodiazepine-10(5H)-carboxylate) (2c)

1,3-bis(bromomethyl)-5-chlorobenzene (1.42 g, 4.80 mmol) was added to a stirred solution of Boc/THP-protected PBD capping unit 1 (4.42 g, 9.60 mmol), TBAI (177 mg, 0.48 mmol) and K₂CO₃ (1.33 g, 9.60 mmol) in dry DMF (55 mL). The reaction mixture was heated to 60° C. and stirred under an argon atmosphere for 1.5 hours at which point analysis by LC/MS revealed substantial product formation at retention time 4.08 min (ES+) m/z 1057 ([M+H]⁺, ˜30% relative intensity). The reaction mixture was allowed to cool to room temperature and the DMF was removed by evaporation in vacuo. The resulting residue was partitioned between water (60 mL) and EtOAc (60 mL) and the aqueous phase was extracted with EtOAc (3×20 mL). The combined organic layers were washed with water (20 mL), brine (40 mL), dried (MgSO₄), filtered and evaporated in vacuo to provide the crude product. Purification by flash chromatography (gradient elution: 50:50 v/v EtOAc/hexane to 80:20 v/v EtOAc/hexane) gave the bis-ether 2c as a white foam (5.10 g, 99% yield).

A catalytic amount of Pd(PPh₃)₄ (5.0 mg, 4.2 μmol) was added to a mixture of the bis-ether 2a (242 mg, 0.21 mmol), propargylamine (41 μL, 35 mg, 0.63 mmol), CuI (1.6 mg, 8.4 μmop, diethylamine (0.42 mL, 309 mg, 4.22 mmol) and oven-dried 4 Å molecular sieve pellets in dry DMF (1.8 mL) in an oven-dried sealable vessel. The mixture was degassed and flushed with argon 3 times then heated in a microwave at 100° C. for 3 minutes at which point analysis by LC/MS revealed complete consumption of starting material and substantial product formation at retention time 3.18 min (ES+) m/z 1076 ([M+H]⁺, ˜60% relative intensity). The reaction mixture was allowed to cool to room temperature and was then filtered through a sinter to remove the sieves (washed with DMF). The filtrate was evaporated in vacuo to provide the unstable crude product 8 which was used immediately in the next step without purification or analysis.

MAL-dPEG®4-acid (88 mg, 0.21 mmol) was added to a stirred solution of EDCI (41 mg, 0.21 mmol) and the crude primary amine 8 in dry DCM (4 mL) at room temperature. The reaction mixture was stirred under an argon atmosphere for 3 hours at which point analysis by LC/MS showed a substantial amount of desired product at retention time 3.58 min (ES+) m/z 1475 ([M+H]′, ˜10% relative intensity), 1498 ([M+Na]⁺, ˜5% relative intensity) accompanied by a side product at retention time 3.85 min. The reaction mixture was diluted with DCM (30 mL) and washed with H₂O (3×10 mL), brine (20 mL), dried (MgSO₄), filtered and evaporated in vacuo to provide the crude product. Purification by flash chromatography (gradient elution: 100% DCM to 96:4 v/v DCM/MeOH) gave the maleimide 9 as a foam (67 mg, 22% yield over 2 steps).

A solution of 95:5 v/v TFA/H₂O (1 mL) was added to a sample of the Boc/THP-protected compound 9 (67 mg, 45.5 μmol) at 0° C. (ice/acetone). After stirring at 0° C. for 1.5 hours, the reaction was deemed complete as judged by LC/MS, desired product peak at retention time 2.67 min (ES+) m/z 1070 ([M+H]⁺, ˜5% relative intensity). The reaction mixture was kept cold and added drop wise to a chilled saturated aqueous solution of NaHCO₃ (50 mL). The mixture was extracted with DCM (3×15 mL) and the combined organic layers washed with brine (40 mL), dried (MgSO₄), filtered and evaporated in vacuo to provide the crude product. Purification by flash chromatography (gradient elution: 100% CHCl₃ to 96:4 v/v CHCl₃/MeOH) gave 10 as an orange foam (12 mg, 24% yield).

B. Alternate Synthesis of Center-Linked PBD Linker Drug Intermediate

The center-linked PBD linker drug intermediate (N-(3-(3,5-bis((((S)-7-methoxy-2-methylene-5-oxo-2,3,5,11a-tetrahydro-1H-pyrrolo[2,1-c][1,4]benzodiazepin-8-yl)oxy)methyl)phenyl)prop-2-yn-1-yl)-1-(3-(2,5-dioxo-2,5-dihydro-1H-pyrrol-1-yl)propanamido)-3,6,9,12-tetraoxapentadecan-15-amide; “10”) having the following formula:

may also be synthesized as follows.

EDCI (263 mg, 1.37 mmol) was added to a stirred solution of t-boc-N-amido-dPEG®₄-acid (26) (500 mg, 1.37 mmol, Stratech Scientific Limited) and propargylamine (88 μL, 76 mg, 1.37 mmol) in dry DCM (10 mL) at room temperature. The reaction mixture was stirred under an argon atmosphere for 16 hours at which point analysis by LC/MS showed a substantial amount of desired product at retention time 1.26 minutes (ES+) m/z 403 ([M+H], ˜50% relative intensity), 425 ([M+Na]⁺, ˜100% relative intensity), note that both starting material and product had weak UV absorption (214 and 254 nm) and were best detected on ES+ TIC. The reaction mixture was diluted with DCM (100 mL) and washed with H₂O (30 mL), brine (40 mL), dried (MgSO₄), filtered and evaporated in vacuo to provide the crude product. Purification by flash chromatography (gradient elution in 1% increments: 100% DCM to 98:2 v/v DCM/MeOH) gave the amide 27 as an oil (392 mg, 71% yield).

A catalytic amount of Pd(PPh₃)₄ (23.0 mg, 19.5 μmol) was added to a mixture of the iodoaryl compound 2a (1.02 g, 0.89 mmol), Boc-acetylene 27 (393 mg, 0.98 mmol), CuI (7.4 mg, 39.1 μmol), diethylamine (2.02 mL, 1.43 g, 19.5 mmol) and oven-dried 4 Å molecular sieve pellets in dry DMF (9 mL) in an oven-dried sealable vessel. The mixture was degassed and flushed with argon 3 times then heated in a microwave at 100° C. for 26 minutes at which point analysis by LC/MS revealed substantial product formation at retention time 1.89 minutes (ES+) m/z 1446 ([M+Na]⁺, ˜100% relative intensity, 1424 ([M+H]⁺, ˜15% relative intensity). The reaction mixture was allowed to cool to room temperature and was then filtered through a sinter to remove the sieves (washed with DMF). The filtrate was evaporated in vacuo and the resulting residue dissolved in DCM (100 mL) and washed with H₂O (20 mL), brine (30 mL), dried (MgSO₄), filtered and evaporated in vacuo to give the crude product. Purification by flash chromatography (gradient elution in 1% increments: 100% DCM to 97:3 v/v DCM/MeOH) provided the alkyne 28 as a yellow foam (882 mg, 70% yield).

TBDMSOTf (1.42 mL, 1.64 g, 6.2 mmol) was added to a stirred solution of the tri-Boc protected compound 28 (882 mg, 0.62 mmol) and 2,6-lutidine (0.96 mL, 883 mg, 8.25 mmol) in dry DCM (15 mL) at room temperature. The reaction mixture was allowed to stir under an argon atmosphere for 16 hours during which time analysis by LC/MS revealed formation of the TBS carbamate at retention time 2.09 minutes (ES+) m/z 1504 ([M+Na]⁺, ˜100% relative intensity). The reaction mixture was diluted with DCM (60 mL) and washed with saturated NH₄Cl (2×20 mL), H₂O (20 mL), brine (30 mL), dried (MgSO₄), filtered and evaporated in vacuo to give the crude TBS carbamate. The product was re-dissolved in THF (15 mL) and treated with a solution of TBAF (744 μL of a 1.0M solution in THF, 0.744 mmol) at room temperature. The reaction mixture was allowed to stir for 1 hour at room temperature at which point analysis by LC/MS revealed substantial product formation at retention time 1.45 minutes (ES+) m/z 1324 ([M+H]⁺, ˜60% relative intensity) along with product corresponding to 1 N10 Boc/1 THP cleaved at retention time 1.29 minutes (ES+) m/z 1121 ([M+H]⁺, ˜10% relative intensity), 1138 ([M+H₂O]⁺, ˜20% relative intensity) and product corresponding to 2 N10 Boc/2 THP cleaved at retention time 1.12 minutes (ES+) m/z 919 ([M+H]⁺, ˜2.5% relative intensity), 937 ([M+H₂O]⁺, ˜3% relative intensity), 955 ([M+2H₂O]⁺, ˜5% relative intensity). The THF was removed by evaporation in vacuo and the resulting residue re-dissolved in DCM (60 mL) and washed with saturated NH₄Cl (2×20 mL), H₂O (20 mL), brine (30 mL), dried (MgSO₄), filtered and evaporated in vacuo to give the key amine 29 as a pinkish foam.

EDCI (61 mg, 0.32 mmol) was added to a stirred solution of N-maleoyl-β-alanine (53 mg, 0.32 mmol) and amine 29 (˜418 mg, 0.32 mmol) in dry DCM (6 mL) at room temperature. The reaction mixture was stirred under an argon atmosphere for 3 hours at which point analysis by LC/MS showed a substantial amount of desired product at retention time 1.80 minutes (ES+) m/z 1474 ([M+H]⁺, ˜15% relative intensity), 1497 ([M+Na]⁺, ˜100% relative intensity), along with product corresponding to 1 N10Boc/1 THP cleaved at retention time 1.56 minutes 1272 ([M+H]⁺, ˜80% relative intensity), 1295 ([M+Na]⁺, ˜45% relative intensity) and product corresponding to 2 N10 Boc/2 THP cleaved at retention time 1.31 minutes (ES+M+ not observed). The reaction mixture was diluted with DCM (30 mL) and washed with H₂O (15 mL), brine (20 mL), dried (MgSO₄), filtered and evaporated in vacuo to provide the crude product 9 as a foam.

A solution of 95:5 v/v TFA/H₂O (5 mL) was added to a crude sample of the Boc/THP-protected compound 9 (˜466 mg, 0.32 mmol) at 0° C. (ice/acetone). After stirring at 0° C. for 1 hour the reaction was deemed complete as judged by LC/MS, desired product peak at retention time 1.32 minutes (ES+) m/z 1070 ([M+H]⁺, ˜100% relative intensity). The reaction mixture was kept cold and added drop-wise to a chilled saturated aqueous solution of NaHCO₃ (120 mL). The mixture was extracted with DCM (3×40 mL) and the combined organic layers washed with brine (50 mL), dried (MgSO₄), filtered and evaporated in vacuo to provide the crude product. Purification by flash chromatography (gradient elution: 100% CHCl₃ to 96:4 v/v CHCl₃/MeOH) gave 10 as an orange foam (202 mg, 60% yield): [α]²¹ _(D)=+351° (c=0.47, CHCl₃); LC/MS (15-minute run), retention time 4.88 minutes (ES+) m/z 1070 ([M+H]⁺, ˜100% relative intensity); ¹H NMR (400 MHz CDCl₃) δ 7.66 (d, 2H, J=4.4 Hz), 7.52 (s, 2H), 7.45-7.40 (m, 3H), 6.98-6.94 (m, 1H), 6.80 (s, 2H), 6.66 (s, 2H), 6.55-6.50 (m, 1H), 5.22-5.07 (m, 8H), 4.30-4.22 (m, 6H), 3.96 (s, 6H), 3.91-3.85 (m, 2H), 3.82 (t, 2H, J=7.2 Hz), 3.76 (t, 2H, J=5.8 Hz), 3.65-3.43 (m, 16H), 3.16-3.08 (m, 2H), 2.94 (d, 2H, J=15.7 Hz), 2.54-2.44 (m, 4H).

C. Conjugation of Linker-Drug Moieties to Antibodies

Hu7C2 antibody-drug conjugates (ADCs) are produced by conjugating hu7C2.v.2.2.LA with a heavy chain A118C mutation (thio-hu7C2-HC A118C) or a light chain K149C mutation (thio-hu7C2-LC-K149C) to the selected drug-linker moiety (e.g., center-linked PBD linker-drug intermediate). As initially isolated, the engineered cysteine residues in antibodies exist as mixed disulfides with cellular thiols (e.g., glutathione) and are thus unavailable for conjugation. Partial reduction of these antibodies (e.g., with DTT), purification, and reoxidation with dehydroascorbic acid (DHAA) gives antibodies with free cysteine sulfhydryl groups available for conjugation, as previously described, e.g., in Junutula et al. (2008) Nat. Biotechnol. 26:925-932 and US 2011/0301334. Briefly, the antibodies are combined with the drug-linker moiety to allow conjugation of the drug-linker moiety to the free cysteine residues of the antibody. After several hours, the ADCs are purified. The drug load (average number of drug moieties per antibody) for the ADC was determined and was in the range of 1.8-1.9. The resulting ADC structures and the terms used for them below are shown in FIG. 6.

An example of a method for conjugation of linker-drug moieties to antibodies is as follows:

Full length, cysteine engineered monoclonal antibodies (THIOMABS™—Junutula, et al., 2008b Nature Biotech., 26(8):925-932; Dornan et al (2009) Blood 114(13):2721-2729; U.S. Pat. No. 7,521,541; U.S. Pat. No. 7,723,485; WO2009/052249, Shen et al (2012) Nature Biotech., 30(2):184-191; Junutula et al (2008) Jour of Immun. Methods 332:41-52) expressed in CHO cells are reduced with about a 20-40 fold excess of TCEP (tris(2-carboxyethyl)phosphine hydrochloride or DTT (dithiothreitol) in 50 mM Tris pH 7.5 with 2 mM EDTA for 3 hrs at 37° C. or overnight at room temperature. (Getz et al (1999) Anal. Biochem. 273:73-80; Soltec Ventures, Beverly, Mass.). The reduced THIOMAB™ is diluted and loaded onto a HiTrap S column in 10 mM sodium acetate, pH 5, and eluted with PBS containing 0.3M sodium chloride. Alternatively, the antibody is acidified by addition of 1/20th volume of 10% acetic acid, diluted with 10 mM succinate pH 5, loaded onto the column and then washed with 10 column volumes of succinate buffer. The column is eluted with 50 mM Tris pH7.5, 2 mM EDTA.

The eluted reduced THIOMAB™ is treated with 15 fold molar excess of DHAA (dehydroascorbic acid) or 200 nM aqueous copper sulfate (CuSO4). Oxidation of the interchain disulfide bonds is complete in about three hours or more. Ambient air oxidation is also effective. The re-oxidized antibody is dialyzed into 20 mM sodium succinate pH 5, 150 mM NaCl, 2 mM EDTA and stored frozen at −20° C.

The deblocked, reoxidized, thio-antibodies (THIOMABS™) are reacted with 6-8 fold molar excess of the selected drug-linker moiety (e.g., center-linked PBD linker-drug intermediate) (from a DMSO stock at a concentration of 20 mM) in 50 mM Tris, pH 8, until the reaction is complete (16-24 hours) as determined by LC-MS analysis of the reaction mixture.

The crude antibody-drug conjugates (ADC) are then applied to a cation exchange column after dilution with 20 mM sodium succinate, pH 5. The column is washed with at least 10 column volumes of 20 mM sodium succinate, pH 5, and the antibody is eluted with PBS. The antibody drug conjugates are formulated into 20 mM His/acetate, pH 5, with 240 mM sucrose using gel filtration columns. The antibody-drug conjugates are characterized by UV spectroscopy to determine protein concentration, analytical SEC (size-exclusion chromatography) for aggregation analysis and LC-MS before and after treatment with Lysine C endopeptidase.

Size exclusion chromatography is performed using a Shodex KW802.5 column in 0.2M potassium phosphate pH 6.2 with 0.25 mM potassium chloride and 15% IPA at a flow rate of 0.75 ml/min. Aggregation state of the conjugate is determined by integration of eluted peak area absorbance at 280 nm.

LC-MS analysis is performed using an Agilent QTOF 6520 ESI instrument. As an example, an antibody-drug conjugate generated using this chemistry is treated with 1:500 w/w Endoproteinase Lys C (Promega) in Tris, pH 7.5, for 30 min at 37° C. The resulting cleavage fragments are loaded onto a 1000A, 8 um PLRP—S column heated to 80° C. and eluted with a gradient of 30% B to 40% B in 5 minutes. Mobile phase A is H₂O with 0.05% TFA and mobile phase B is acetonitrile with 0.04% TFA. The flow rate is 0.5 ml/min. Protein elution is monitored by UV absorbance detection at 280 nm prior to electrospray ionization and MS analysis. Chromatographic resolution of the unconjugated Fc fragment, residual unconjugated Fab and drugged Fab is usually achieved. The obtained m/z spectra were deconvoluted using Mass Hunter™ software (Agilent Technologies) to calculate the mass of the antibody fragments.

Example 3: Efficacy of hu7C2 Antibody Drug Conjugates in MMTV-Her2 Fo5 Transgenic Mammary Tumor Transplant Xenograft Models

CRL nu/nu mice (Charles River Laboratory) were implanted with ˜2×2 mm fragments of MMTV-Her2 Fo5 transgenic breast tumors. When tumors reached a mean tumor volume of 100-300 mm³, animals were grouped into 7 groups of 8 mice each. The mice received a single administration on day 1 of one of the following treatments, via intravenous tail vein injection: (1) vehicle (20 mM L-histidine, 240 mM sucrose, 0.02% Tween-20, pH 5.5), (2)thio-hu7C2-HC-A118C-center-linked-PBD, 0.3 mg/kg; (3) thio-hu7C2-HC-A118C-center-linked-PBD, 1 mg/kg; (4) thio-hu7C2-LC-K149C-center-linked-PBD, 0.3 mg/kg; (5) thio-hu7C2-LC-K149C-center-linked-PBD, 1 mg/kg; (6) thio-controlAb-HC-A118C-center-linked-PBD, 1 mg/kg; or (7) thio-controlAb-LC-K149C-center-linked-PBD, 1 mg/kg. The DAR for the thio-hu7C2-LC-K149C-center-linked-PBD, the thio-hu7C2-HC-A118C-center-linked-PBD, and the thio-controlAb-LC-K149C-center-linked-PBD was 1.8. The DAR for the thio-controlAb-HC-A118C-center-linked-PBD was 1.9.

Tumor and body weight measurements were taken at least once per week for the duration of the study. Mice were euthanized when tumors reached 1000-2000 mm³ or if the mouse lost 20% or more of its body weight. Tumor volume was measured in two dimensions (length and width) using calipers and the tumor volume was calculated using the formula: Tumor size (mm³)=(longer measurement×shorter measurement²)×0.5.

The results of that experiment are shown in Table 5 and FIG. 4. Each group contained 8 mice at the beginning of the study. AUC/day % TGI (tumor growth inhibition) is calculated using the following formula: % TGI=100×(1−AUCtreatment/Day+AUCvehicle/Day). PR=partial response, which is defined as more than 50% but less than 100% reduction in tumor volume, compared with the starting tumor volume, on any day during the study. CR=complete response, which is defined as a 100% reduction in tumor volume (no measurable tumor), on any day during the study.

TABLE 5 Efficacy of hu7C2 ADCs in MMTV-Her2 Fo5 transgenic mammary tumor xenograft model tumor volume, Last Day AUC/day % TGI % BW change, Group last day (N) (lower, upper) PR CR last day (1) vehicle 1640 14 (7) 0 (0, 0) 0 0 5.71 (2) thio-hu7C2-HC- 260 35 (6) 93 (77, 103) 1 0 2.18 A118C-center-linked- PBD, 0.3 mg/kg (3) thio-hu7C2-HC- 115 43 (6) 106 (95, 118) 2 2 5.83 A118C- center-linked- PBD, 1 mg/kg (4) thio-hu7C2-LC- 194 43 (6) 97 (82, 107) 2 0 5.15 K149C-center-linked- PBD, 0.3 mg/kg (5) thio-hu7C2-LC- 67 43 (8) 111 (101, 123) 5 3 3.53 K149C-center-linked- PBD, 1 mg/kg (6) thio-controlAb-HC- 794 22 (8) 54 (10, 79) 0 0 7.66 A118C-center-linked- PBD, 1 mg/kg (7) thio-controlAb-LC- 512 26 (6) 72 (39, 89) 0 0 4.62 K149C-center-linked- PBD, 1 mg/kg

As shown in Table 5, thio-hu7C2-LC-K149C-center-linked-PBD showed 5 partial responses and 3 complete responses at 1 mg/kg and 2 partial responses at 0.3 mg/kg. Thio-hu7C2-HC-A118C-disulfide-PBD showed 2 partial responses and 2 complete responses at 1 mg/kg and 1 partial response at 0.3 mg/kg.

Example 4: Efficacy of hu7C2 Antibody Drug Conjugates in KPL-4 Human Breast Cancer Transgenic Mammary Tumor Transplant Xenograft Models

Female C.B-17 SCID-beige mice (Charles River Laboratory) were each inoculated in the thoracic mammary fat pad area with 3 million KPL-4 cells suspended in HBSS/matrigel (1:1 ratio). When the xenograft tumors reached an average tumor volume of 100-300 mm3 (referred to as Day 0), animals were randomized into 5 groups of 8 mice each. The mice received a single administration on day 1 of one of the following treatments, via intravenous tail vein injection: (1) vehicle (20 mM L-histidine, 240 mM sucrose, 0.02% Tween-20, pH 5.5), (2) thio-hu7C2-LC-K149C-center-linked-PBD, 0.3 mg/kg; (3) thio-hu7C2-LC-K149C-center-linked-PBD, 1 mg/kg; (4) thio-hu7C2-LC-K149C-center-linked-PBD, 3 mg/kg; (5) thio-controlAb-LC-K149C-center-linked-PBD, 3 mg/kg. The DAR for the thio-hu7C2-LC-K149C-center-linked-PBD was 1.7 and the DAR for the control was 1.8.

Tumors and body weights of mice were measured 1-2 times a week throughout the study. Mice were promptly euthanized when body weight loss was >20% of their starting weight. Tumor volume was measured in two dimensions (length and width) using calipers and the tumor volume was calculated using the formula: Tumor size (mm3)=(longer measurement×shorter measurement2)×0.5.

The results of that experiment are shown in Table 6 and FIG. 5. Each group contained 8 mice at the beginning of the study. AUC/day % TGI (tumor growth inhibition) is calculated using the following formula: % TGI=100×(1−AUCtreatment/Day+AUCvehicle/Day). PR=partial response, which is defined as more than 50% but less than 100% reduction in tumor volume, compared with the starting tumor volume, on any day during the study. CR=complete response, which is defined as a 100% reduction in tumor volume (no measurable tumor), on any day during the study.

TABLE 6 Efficacy of hu7C2 ADCs in KPL-4 Human Breast Cancer Transgenic Mammary Tumor Transplant Xenograft Models tumor volume, Last Day AUC/day % TGI % BW change, Group last day (N) (lower, upper) PR CR last day (1) vehicle 1095 22 (8) 0 (0, 0) 0 0 −5.89 (2) thio-hu7C2-HC- 550 25 (8) 58 (−14, 87) 0 0 −2.45 A149C-center-linked- PBD, 0.3 mg/kg (3) thio-hu7C2-HC- 641 25 (7) 55 (−28, 90) 0 0 −5.7 A149C-center-linked- PBD, 1 mg/kg (4) thio-hu7C2-HC- 79 25 (8) 120 (108, 147) 5 1 −5.94 A149C-center-linked- PBD, 3 mg/kg (5) thio-controlAb-LC- 247 25 (6) 107 (87, 128) 1 0 −14.99 K149C-center-linked- PBD, 3 mg/kg

As shown in Table 6, thio-hu7C2-LC-K149C-center-linked-PBD showed 5 partial responses and 1 complete response at 1 mg/kg.

In this study, anti-Her2 ADC demonstrated dose-dependent inhibition of tumor growth, resulting in tumor regression at 3 mg/kg dose.

Example 3: Crystal Structure of 7C2 Fab Bound to HER2 Methods

Expression, Purification, and Crystallization of the 7C2/HER2 Complex

7C2 Fab was expressed in E. coli and purified using Protein G sepharose affinity resin (GE), SP sepharose cation exchange chromatography, and size exclusion chromatography (SEC). HER2 extracellular domain (ECD) was expressed in CHO cells and purified by affinity chromatography using trastuzumab antibody linked to controlled pore glass beads, followed by DEAE anion exchange and size exclusion chromatography.

The complex between Fab 7C2 and HER2 ECD was purified by SEC. The complex was deglycosylated using a combination of enzymes (Endo F1, F2, F3, Endo H and PNGase), followed by purification by SEC into 0.1M NaCl, 20 mM HEPES pH 7.2 and 2% glycerol. The complex was crystallized resulting in thick plates after one week in hanging drops using equal parts of protein at 10 mg/mL and reservoir (30% v/v PEG 550 monomethylether, 0.1M Sodium citrate tribasic dihydrate pH 5.0) and treated briefly with reservoir prior to immersion in liquid nitrogen.

The diffraction data for the complex extending to 2.7 Å resolution were collected at ˜110 K at SSRL beam line 11-1. The diffraction images were integrated and scaled using the program HKL2000 and elements of the CCP4 suite. See Winn et al., 2011, Acta Crystallogr D. Biol. Crystallogr. 67: 235-42.

The structure was solved by molecular replacement (MR) using program Phaser. See McCoy et al., 2005, Acta Crystallogr D. Biol. Crystallogr. 61: 458-64. The MR search models include the HER2 ECD domain derived from a crystal structure of HER2/Herceptin Fab complex (PDB code: 1N8Z), Fab constant domain (PDB code: 1N8Z) and a predicted model for the variable domain generated by the program Modeller. See Fiser et al., 2003, Methods Enzymol., 374: 461-91. The structure was refined with programs REFMACS (Marshudov et al., 2011, Acta Crystallogr D. Biol. Crystallogr. 67: 355-67) and PHENIX.refine (Adams et al., 2010, Acta Crystallogr D. Biol. Crystallogr. 66 (pt. 2): 213-21) using the maximum likelihood target functions, anisotropic individual B-factors, and TLS refinement. The data and refinement statistics are summarized in Table 7.

TABLE 7 Statistics of x-ray diffraction data collection and structure refinement (values in parentheses are for last resolution shell) Data collection SSRL 11-1 Space group C222₁ Cell parameters (Å) a = 136.8, b = 171.9, c = 162.5 Resolution (Å) 50-2.75 (2.85-2.75) Rsym 0.112 (0.689) Number of observations 319169 Unique reflections 49078 Redundancy 6.5 (5.5) Completeness (%) 98.8 (92.2) <I>/<σI> 20 (2.2) Vm(A³/Da) 4.2 Refinement Resolution (Å) 48.33-2.75 Number of reflections 49053 R, Rfree 0.23, 0.25 Number of residues 1047 Number of waters 109 Number of atoms 8039 RMSD bonds (Å) 0.007 RMSD angles (°) 1.2 Mean bonded ΔB (Å²) 5.5 Ramachandran analysis (%) 93/6/1 Number of TLS groups 3 <B>^(e) (Å²) 7C2/HER2 88

Results

The crystal structure of the 7C2 Fab/HER2 complex was determined at 2.75 Å resolution. Each asymmetric unit cell contains one Fab/HER2 complex. The structure revealed that the 7C2 Fab binds to domain I of HER2 ECD (FIG. 11A). The binding epitope is distinct from those in the previously characterized complexes of HER2 ECD with Fab fragments of therapeutic antibodies trastuzumab (Tmab) or pertuzumab (Pmab), which are located at domains IV and II, respectively. See, e.g., Cho et al., 2003, Nature, 421: 756-60; Eigenbrot et al., 2010, PNAS, 107: 15039-44; and Franklin et al., 2004, Cancer Cell, 5: 17-28. Indeed, an overlay of the 7C2 Fab/HER2 ECD complex structure with the structures of Tmab/HER2 ECD complex and Pmab/HER2 ECD complex shows that the three Fabs have independent, non-overlapping epitopes and would not spatially interfere with each other binding to HER2 (FIG. 11A). A superposition of the HER2 ECD structures within the Tmab/HER2 ECD complex, Pmab/HER2 ECD complex and 7C2 Fab/HER2 ECD complex showed a minimal structural differences (FIG. 11B). This observation suggested that the HER2 ECD is relatively rigid, which is consistent with previous reports in the literature. See, e.g., Cho et al., 2003, Nature, 421: 756-60; Eigenbrot et al., 2010, PNAS, 107: 15039-44; and Franklin et al., 2004, Cancer Cell, 5: 17-28.

The 7C2 Fab binds to the loop 163-175 and the loop 185-189 within the HER2 domain I (i.e., amino acids 163-175 and 185-189 of mature HER2, e.g., SEQ ID NO: 39; domain I is shown in SEQ ID NO: 35). The binding buries ˜1160 Å² of solvent accessible surface area on each side of the interface. There is an intricate network of hydrophobic, hydrogen bonding and ionic interactions. Certain residues that are involved in binding are labeled in FIG. 11C. The side chain of His171 makes contacts with the heavy chain residues His52 and Asp55. The HER2 residues Ser186, Ser187 and Glu188 form hydrogen bonding with the D102 from heavy chain and the two Tyr residues (Tyr36 and Tyr54) from the light chain.

The 7C2 binding epitope partially overlaps with that from a previously reported anti-HER2 antibody, chA21 (FIG. 11D). See Zhou et al., 2011, JBC, 286: 31676-83. Both epitopes include a loop in domain I (residues 163-187). Interestingly, the residue His171 plays a role in the interaction with both antibodies. However, the chA21 binding epitope spans ˜1820 Å² of solvent accessible surface area, which is ˜660 Å² bigger than the 7C2 epitope and includes two additional N-terminal loops, residues 100-105 and residues 135-144.

Although the foregoing invention has been described in some detail by way of illustration and example for purposes of clarity of understanding, the descriptions and examples should not be construed as limiting the scope of the invention. The disclosures of all patent and scientific literature cited herein are expressly incorporated in their entirety by reference.

Table of Sequences SEQ NAME SEQUENCE ID NO Human Her2 MELAALCRWG LLLALLPPGA ASTQVCTGTD MKLRLPASPE THLDMLRHLY  1 precursor QGCQVVQGNL ELTYLPTNAS LSFLQDIQEV QGYVLIAHNQ VRQVPLQRLR (UniProtKB/ IVRGTQLFED NYALAVLDNG DPLNNTTPVT GASPGGLREL QLRSLTEILK Swiss-Prot: GGVLIQRNPQ LCYQDTILWK DIFHKNNQLA LTLIDTNRSR ACHPCSPMCK P04626.1); aa 1- GSRCWGESSE DCQSLTRTVC AGGCARCKGP LPTDCCHEQC AAGCTGPKHS 22 signal DCLACLHFNH SGICELHCPA LVTYNTDTFE SMPNPEGRYT FGASCVTACP sequence; aa 23- YNYLSTDVGS CTLVCPLHNQ EVTAEDGTQR CEKCSKPCAR VCYGLGMEHL 1255 mature REVRAVTSAN IQEFAGCKKI FGSLAFLPES FDGDPASNTA PLQPEQLQVF Her2 ETLEEITGYL YISAWPDSLP DLSVFQNLQV IRGRILHNGA YSLTLQGLGI SWLGLRSLRE LGSGLALIHH NTHLCFVHTV PWDQLFRNPH QALLHTANRP EDECVGEGLA CHQLCARGHC WGPGPTQCVN CSQFLRGQEC VEECRVLQGL PREYVNARHC LPCHPECQPQ NGSVTCFGPE ADQCVACAHY KDPPFCVARC PSGVKPDLSY MPIWKFPDEE GACQPCPINC THSCVDLDDK GCPAEQRASP LTSIISAVVG ILLVVVLGVV FGILIKRRQQ KIRKYTMRRL LQETELVEPL TPSGAMPNQA QMRILKETEL RKVKVLGSGA FGTVYKGIWI PDGENVKIPV AIKVLRENTS PKANKEILDE AYVMAGVGSP YVSRLLGICL TSTVQLVTQL MPYGCLLDHV RENRGRLGSQ DLLNWCMQIA KGMSYLEDVR LVHRDLAARN VLVKSPNHVK ITDFGLARLL DIDETEYHAD GGKVPIKWMA LESILRRRFT HQSDVWSYGV TVWELMTFGA KPYDGIPARE IPDLLEKGER LPQPPICTID VYMIMVKCWM IDSECRPRFR ELVSEFSRMA RDPQRFVVIQ NEDLGPASPL DSTFYRSLLE DDDMGDLVDA EEYLVPQQGF FCPDPAPGAG GMVHHRHRSS STRSGGGDLT LGLEPSEEEA PRSPLAPSEG AGSDVFDGDL GMGAAKGLQS LPTHDPSPLQ RYSEDPTVPL PSETDGYVAP LTCSPQPEYV NQPDVRPQPP SPREGPLPAA RPAGATLERP KTLSPGKNGV VKDVFAFGGA VENPEYLTPQ GGAAPQPHPP PAFSPAFDNL YYWDQDPPER GAPPSTFKGT PTAENPEYLG LDVPV mature human TQVCTGTD MKLRLPASPE THLDMLRHLY QGCQVVQGNL ELTYLPTNAS 39 HER2 LSFLQDIQEV QGYVLIAHNQ VRQVPLQRLR IVRGTQLFED NYALAVLDNG DPLNNTTPVT GASPGGLREL QLRSLTEILK GGVLIQRNPQ LCYQDTILWK DIFHKNNQLA LTLIDTNRSR ACHPCSPMCK GSRCWGESSE DCQSLTRTVC AGGCARCKGP LPTDCCHEQC AAGCTGPKHS DCLACLHFNH SGICELHCPA LVTYNTDTFE SMPNPEGRYT FGASCVTACP YNYLSTDVGS CTLVCPLHNQ EVTAEDGTQR CEKCSKPCAR VCYGLGMEHL REVRAVTSAN IQEFAGCKKI FGSLAFLPES FDGDPASNTA PLQPEQLQVF ETLEEITGYL YISAWPDSLP DLSVFQNLQV IRGRILHNGA YSLTLQGLGI SWLGLRSLRE LGSGLALIHH NTHLCFVHTV PWDQLFRNPH QALLHTANRP EDECVGEGLA CHQLCARGHC WGPGPTQCVN CSQFLRGQEC VEECRVLQGL PREYVNARHC LPCHPECQPQ NGSVTCFGPE ADQCVACAHY KDPPFCVARC PSGVKPDLSY MPIWKFPDEE GACQPCPINC THSCVDLDDK GCPAEQRASP LTSIISAVVG ILLVVVLGVV FGILIKRRQQ KIRKYTMRRL LQETELVEPL TPSGAMPNQA QMRILKETEL RKVKVLGSGA FGTVYKGIWI PDGENVKIPV AIKVLRENTS PKANKEILDE AYVMAGVGSP YVSRLLGICL TSTVQLVTQL MPYGCLLDHV RENRGRLGSQ DLLNWCMQIA KGMSYLEDVR LVHRDLAARN VLVKSPNHVK ITDFGLARLL DIDETEYHAD GGKVPIKWMA LESILRRRFT HQSDVWSYGV TVWELMTFGA KPYDGIPARE IPDLLEKGER LPQPPICTID VYMIMVKCWM IDSECRPRFR ELVSEFSRMA RDPQRFVVIQ NEDLGPASPL DSTFYRSLLE DDDMGDLVDA EEYLVPQQGF FCPDPAPGAG GMVHHRHRSS STRSGGGDLT LGLEPSEEEA PRSPLAPSEG AGSDVFDGDL GMGAAKGLQS LPTHDPSPLQ RYSEDPTVPL PSETDGYVAP LTCSPQPEYV NQPDVRPQPP SPREGPLPAA RPAGATLERP KTLSPGKNGV VKDVFAFGGA VENPEYLTPQ GGAAPQPHPP PAFSPAFDNL YYWDQDPPER GAPPSTFKGT PTAENPEYLG LDVPV Murine 7C2.B9 DIVLTQSPAS LVVSLGQRAT ISCRASQSVS GSRFTYMHWY QQKPGQPPKL  2 (mu7C2) light LIKYASILES GVPARFSGGG SGTDFTLNIH PVEEDDTATY YCQHSWEIPP chain variable WTFGGGTKLE IK region Mu7C2 heavy QVQLQQPGAE LVRPGASVKL SCKASGYSFT GYWMNWLKQR PGQGLEWIGM  3 chain variable IHPSDSEIRA NQKFRDKATL TVDKSSTTAY MQLSSPTSED SAVYYCARGT region YDGGFEYWGQ GTTLTVSS Mu7C2 HVR-L1 RASQSVSGSRFTYMH  4 Mu7C2 HVR-L2 YASILES  5 Mu7C2 HVR-L3 QHSWEIPPWT  6 Mu7C2 HVR-H1 GYWMN  7 Mu7C2 HVR-H2 MIHPSDSEIRANQKFRD  8 Mu7C2 HVR-H3 GTYDGGFEY  9 Humanized DIVMTQSPDS LAVSLGERAT INCRASQSVS GSRFTYMHWY QQKPGQPPKL 10 7C2.v2.2.LA LIKYASILES GVPDRFSGSG SGTDFTLTIS SLQAEDVAVY YCQHSWEIPP (″hu7C2″) light WTFGQGTKVE IK chain variable region Hu7C2 heavy EVQLVQSGAE VKKPGASVKV SCKASGYSFT GYWMNWVRQA PGQGLEWIGM 11 chain variable IHPLDAEIRA NQKFRDRVTI TVDTSTSTAY LELSSLRSED TAVYYCARGT region YDGGFEYWGQ GTLVTVSS Hu7C2 HVR-L1 RASQSVSGSRFTYMH 12 Hu7C2 HVR-L2 YAILES 13 Hu7C2 HVR-L3 QHSWEIPPWT 14 Hu7C2 HVR-H1 GYWMN 15 Hu7C2 HVR-H2 MIHPLDAEIRANQKFRD 16 (Hu7C2. v2.1.S53L, S55A HVR-H2) Hu7C2 HVR-H3 GTYDGGFEY 17 Humanized DIVMTQSPDS LAVSLGERAT INCRASQSVS GSRFTYMHWY QQKPGQPPKL 18 7C2.v2.2.LA LIKYASILES GVPDRFSGSG SGTDFTLTIS SLQAEDVAVY YCQHSWEIPP (hu7C2) kappa WTFGQGTKVE IKRTVAAPSV FIFPPSDEQL KSGTASVVCL LNNFYPREAK light chain VQWKVDNALQ SGNSQESVTE QDSKDSTYSL SSTLTLSKAD YEKHKVYACE VTHQGLSSPV TKSFNRGEC Hu7C2IgG1 EVQLVQSGAE VKKPGASVKV SCKASGYSFT GYWMNWVRQA PGQGLEWIGM 19 heavy chain IHPLDAEIRA NQKFRDRVTI TVDTSTSTAY LELSSLRSED TAVYYCARGT YDGGFEYWGQ GTLVTVSSAS TKGPSVFPLA PSSKSTSGGT AALGCLVKDY FPEPVTVSWN SGALTSGVHT FPAVLQSSGL YSLSSVVTVP SSSLGTQTYI CNVNHKPSNT KVDKKVEPKS CDKTHTCPPC PAPELLGGPS VFLFPPKPKD TLMISRTPEV TCVVVDVSHE DPEVKFNWYV DGVEVHNAKT KPREEQYNST YRVVSVLTVL HQDWLNGKEY KCKVSNKALP APIEKTISKA KGQPREPQVY TLPPSREEMT KNQVSLTCLV KGFYPSDIAV EWESNGQPEN NYKTTPPVLD SDGSFFLYSK LTVDKSRWQQ GNVFSCSVMH EALHNHYTQK SLSLSPGK Hu7C2. MIHPMDSEIRANQKFRD 20 v2.1.S53M HVR- H2 Hu7C2. MIHPLDSEIRANQKFRD 21 v2.1.S53L HVR- H2 Hu7C2. GTYDGGFKY 22 v2.1.E101K HVR-H3 Humanized DIVMTQSPDS LAVSLGERAT INCRASQSVS GSRFTYMHWY QQKPGQPPKL 23 7C2.v2.2.LA LIKYASILES GVPDRFSGSG SGTDFTLTIS SLQAEDVAVY YCQHSWEIPP (hu7C2) K149C WTFGQGTKVE IKRTVAAPSV FIFPPSDEQL KSGTASVVCL LNNFYPREAK kappa light VQWCVDNALQ SGNSQESVTE QDSKDSTYSL SSTLTLSKAD YEKHKVYACE chain VTHQGLSSPV TKSFNRGEC Hu7C2 A118C EVQLVQSGAE VKKPGASVKV SCKASGYSFT GYWMNWVRQA PGQGLEWIGM 24 IgG1 heavy chain IHPLDAEIRA NQKFRDRVTI TVDTSTSTAY LELSSLRSED TAVYYCARGT YDGGFEYWGQ GTLVTVSSCS TKGPSVFPLA PSSKSTSGGT AALGCLVKDY FPEPVTVSWN SGALTSGVHT FPAVLQSSGL YSLSSVVTVP SSSLGTQTYI CNVNHKPSNT KVDKKVEPKS CDKTHTCPPC PAPELLGGPS VFLFPPKPKD TLMISRTPEV TCVVVDVSHE DPEVKFNWYV DGVEVHNAKT KPREEQYNST YRVVSVLTVL HQDWLNGKEY KCKVSNKALP APIEKTISKA KGQPREPQVY TLPPSREEMT KNQVSLTCLV KGFYPSDIAV EWESNGQPEN NYKTTPPVLD SDGSFFLYSK LTVDKSRWQQ GNVFSCSVMH EALHNHYTQK SLSLSPGK V205C cysteine TVAAPSVFIF PPSDEQLKSG TASVVCLLNN FYPREAKVQW KVDNALQSGN 25 engineered light SQESVTEQDS KDSTYSLSST LTLSKADYEK HKVYACEVTH QGLSSPCTKS chain constant FNRGEC region (Igκ) A118C cysteine CSTKGPSVFP LAPSSKSTSG GTAALGCLVK DYFPEPVTVS WNSGALTSGV 26 engineered heavy HTFPAVLQSS GLYSLSSVVT VPSSSLGTQT YICNVNHKPS NTKVDKKVEP chain constant KSCDKTHTCP PCPAPELLGG PSVFLFPPKP KDTLMISRTP EVTCVVVDVS region (IgG1) HEDPEVKFNW YVDGVEVHNA KTKPREEQYN STYRVVSVLT VLHQDWLNGK EYKCKVSNKA LPAPIEKTIS KAKGQPREPQ VYTLPPSREE MTKNQVSLTC LVKGFYPSDI AVEWESNGQP ENNYKTTPPV LDSDGSFFLY SKLTVDKSRW QQGNVFSCSV MHEALHNHYT QKSLSLSPGK K149C cysteine TVAAPSVFIF PPSDEQLKSG TASVVCLLNN FYPREAKVQW CVDNALQSGN 27 engineered light SQESVTEQDS KDSTYSLSST LTLSKADYEK HKVYACEVTH QGLSSPVTKS chain constant FNRGEC region (Igκ) S400C cysteine ASTKGPSVFP LAPSSKSTSG GTAALGCLVK DYFPEPVTVS WNSGALTSGV 28 engineered heavy HTFPAVLQSS GLYSLSSVVT VPSSSLGTQT YICNVNHKPS NTKVDKKVEP chain constant KSCDKTHTCP PCPAPELLGG PSVFLFPPKP KDTLMISRTP EVTCVVVDVS region (IgG1) HEDPEVKFNW YVDGVEVHNA KTKPREEQYN STYRVVSVLT VLHQDWLNGK EYKCKVSNKA LPAPIEKTIS KAKGQPREPQ VYTLPPSREE MTKNQVSLTC LVKGFYPSDI AVEWESNGQP ENNYKTTPPV LDCDGSFFLY SKLTVDKSRW QQGNVFSCSV MHEALHNHYT QKSLSLSPGK 

1. An immunoconjugate comprising an antibody and a cytotoxic agent, wherein the immunoconjugate has the formula Ab-(L-D)p, wherein: (a) Ab is the antibody; (b) L is a linker; (c) D is a cytotoxic agent; and (d) p ranges from 1-8; and wherein D is a pyrrolobenzodiazepine and L-D is of Formula A:

wherein: R² is

 where R^(36a) and R^(36b) are independently selected from H, F, C₁₋₄ saturated alkyl, C₂₋₃ alkenyl, which alkyl and alkenyl groups are optionally substituted by a group selected from C₁₋₄ alkyl amido and C₁₋₄ alkyl ester; or, when one of R^(36a) and R^(36b) is H, the other is selected from nitrile and a C₁₋₄ alkyl ester; R⁶ and R⁹ are independently selected from H, R, OH, OR, SH, SR, NH₂, NHR, NRR′, NO₂, Me₃Sn and halo; R⁷ is independently selected from H, R, OH, OR, SH, SR, NH₂, NHR, NRR′, NO₂, Me₃Sn and halo; Y has the formula:

G is a linker connected to the antibody; n is an integer selected in the range of 0 to 48; R^(A4) is a C₁₋₆ alkylene group; either: (a) R¹⁰ is H, and R¹¹ is OH, OR^(A), where R^(A) is C₁₋₄ alkyl; or (b) R¹⁰ and R¹¹ form a nitrogen-carbon double bond between the nitrogen and carbon atoms to which they are bound; or (c) R¹⁰ is H and R¹¹ is OSO_(z)M, where z is 2 or 3 and M is a monovalent pharmaceutically acceptable cation; R and R′ are each independently selected from optionally substituted C₁₋₁₂ alkyl, C₃₋₂₀ heterocyclyl and C₅₋₂₀ aryl groups, and optionally in relation to the group NRR′, R and R′ together with the nitrogen atom to which they are attached form an optionally substituted 4-, 5-, 6- or 7-membered heterocyclic ring; R¹⁶, R¹⁷, R¹⁹, R²⁰, R²¹ and R²² are as defined for R⁶, R⁷, R⁹, R¹⁰, R¹¹ and R² respectively; Z is CH or N; T and T′ are independently selected from a single bond or a C₁₋₉ alkylene, which chain may be interrupted by one or more heteroatoms, e.g., O, S, N(H), NMe, provided that the number of atoms in the shortest chain of atoms between X and X′ is 3 to 12 atoms; and X and X′ are independently selected from O, S and N(H); and wherein the antibody is an antibody that binds HER2 comprising (a) HVR—H1 comprising the amino acid sequence of SEQ ID NO:15; (b) HVR—H2 comprising the amino acid sequence of SEQ ID NO:16; (c) HVR—H3 comprising the amino acid sequence of SEQ ID NO:17; (d) HVR-L1 comprising the amino acid sequence of SEQ ID NO:12; (e) HVR-L2 comprising the amino acid sequence of SEQ ID NO:13; and (f) HVR-L3 comprising the amino acid sequence of SEQ ID NO:14.
 2. The immunoconjugate of claim 1, wherein the antibody comprises a heavy chain variable region comprising the sequence of SEQ ID NO: 11 and a light chain variable region comprising the sequence of SEQ ID NO:
 10. 3. The immunoconjugate of claim 1, which is a monoclonal antibody.
 4. The immunoconjugate of claim 3, which is a humanized or chimeric antibody.
 5. The immunoconjugate of claim 1, which is an antibody fragment that binds HER2.
 6. The immunoconjugate of claim 1, wherein HER2 is human HER2 comprising amino acids 23 to 1255 of SEQ ID NO:
 1. 7. The immunoconjugate of claim 1, wherein the antibody binds to extracellular domain I of HER2.
 8. The immunoconjugate of claim 7, wherein extracellular domain I of HER2 has the sequence of SEQ ID NO:
 35. 9. The immunoconjugate of claim 4, which is an IgG1, IgG2a or IgG2b antibody.
 10. The immunoconjugate of claim 1, wherein the antibody comprises one or more engineered free cysteine amino acids residues.
 11. The immunoconjugate of claim 10, wherein the one or more engineered free cysteine amino acids residues are located in the heavy chain.
 12. The immunoconjugate of claim 10, wherein the one or more engineered free cysteine amino acids residues are located in the light chain.
 13. The immunoconjugate of claim 11, wherein the antibody comprises at least one mutation in the heavy chain constant region selected from A118C and S400C.
 14. The immunoconjugate of claim 12, wherein the antibody comprises at least one mutation in the light chain constant region selected from K149C and V205C.
 15. The immunoconjugate of claim 1, wherein the antibody comprises: a) a heavy chain comprising the sequence of SEQ ID NO: 19 and a light chain comprising the sequence of SEQ ID NO: 18; or b) a heavy chain comprising the sequence of SEQ ID NO: 19 and a light chain comprising the sequence of SEQ ID NO: 23; or c) a heavy chain comprising the sequence of SEQ ID NO: 24 and a light chain comprising the sequence of SEQ ID NO:
 18. 16. The immunoconjugate of claim 1, wherein the antibody comprises the heavy chain constant region of SEQ ID NO:
 28. 17. The immunoconjugate of claim 1, wherein the antibody comprises the light chain constant region of SEQ ID NO:
 25. 18. The immunoconjugate of claim 1, wherein R⁹ is H.
 19. The immunoconjugate of claim 1, wherein R⁶ is H.
 20. The immunoconjugate of claim 1, wherein R⁷ is OR^(7A), where R^(7A) is optionally substituted C₁₋₄ alkyl.
 21. The immunoconjugate of claim 1, wherein R^(7A) is Me.
 22. The immunoconjugate of claim 1, wherein X is O.
 23. The immunoconjugate of claim 1, wherein T is selected from a single bond, C₁, and a C₂ alkylene group.
 24. The immunoconjugate of claim 1, wherein T is a C₁ alkylene group.
 25. The immunoconjugate of claim 1, wherein R^(36a) and R^(36b) are both H.
 26. The immunoconjugate of claim 1, wherein R^(36a) and R^(36b) are both methyl.
 27. The immunoconjugate of claim 1, wherein one of R^(36a) and R^(36b) is H, and the other is selected from C₁₋₄ saturated alkyl, C₂₋₃ alkenyl, which alkyl and alkenyl groups are optionally substituted.
 28. The immunoconjugate of claim 1, wherein the group of R^(36a) and R^(36b) which is not H is selected from methyl and ethyl.
 29. The immunoconjugate of claim 1, wherein R¹⁰ is H, and R¹¹ is OH.
 30. The immunoconjugate of claim 1, wherein R¹⁰ and R¹¹ form a nitrogen-carbon double bond between the nitrogen and carbon atoms to which they are bound.
 31. The immunoconjugate of claim 1, wherein R¹⁶, R¹⁷, R¹⁹, R²⁰, R²¹, R²², X′ and T′ are the same as R⁶, R⁷, R⁹, R¹⁰, R², and T, respectively.
 32. The immunoconjugate of claim 1, comprising the structure:


33. The immunoconjugate of claim 32, comprising the structure:


34. The immunoconjugate of claim 1, wherein p ranges from 1.3-2 or from 2-5.
 35. A pharmaceutical formulation comprising the immunoconjugate of claim 1 and a pharmaceutically acceptable carrier.
 36. The pharmaceutical formulation of claim 35, further comprising an additional therapeutic agent.
 37. The pharmaceutical formulation of claim 36, wherein the additional therapeutic agent is an antibody or immunoconjugate that binds HER2.
 38. The pharmaceutical formulation of claim 37, wherein the additional therapeutic agent is (i) an antibody or immunoconjugate that binds to domain II of HER2, and/or (ii) an antibody or immunoconjugate that binds to domain IV or HER2.
 39. The pharmaceutical formulation of claim 38, wherein the additional therapeutic agent is (i) an antibody or immunoconjugate that binds to epitope 2C4, and/or (ii) an antibody or immunoconjugate that binds to epitope 4D5.
 40. The pharmaceutical formulation of claim 36, wherein the additional therapeutic agent is trastuzumab, trastuzumab-MCC-DM1 (T-DM1), and/or pertuzumab.
 41. The pharmaceutical formulation of claim 36, further comprising (1) trastuzumab or T-DM1, and (2) pertuzumab.
 42. A method of treating an individual having a HER2-positive cancer, the method comprising administering to the individual an effective amount of the immunoconjugate of claim
 1. 43. The method of claim 42, wherein the HER2-positive cancer is breast cancer or gastric cancer.
 44. The method of claim 43, wherein the HER2-positive breast cancer is early-stage breast cancer.
 45. The method of claim 43, wherein the HER2-positive breast cancer is metastatic breast cancer.
 46. The method of claim 42, further comprising administering an additional therapeutic agent to the individual.
 47. A method of treating an individual having a HER2-positive cancer, the method comprising administering to the individual an effective amount of the immunoconjugate of claim 1 and at least one additional therapeutic agent to the individual.
 48. The method of claim 47, wherein the additional therapeutic agent is an antibody or immunoconjugate that binds HER2.
 49. The method of claim 48, wherein the additional therapeutic agent is (i) an antibody or immunoconjugate that binds to domain II of HER2, and/or (ii) an antibody or immunoconjugate that binds to domain IV or HER2.
 50. The method of claim 49, wherein the additional therapeutic agent is (i) an antibody or immunoconjugate that binds to epitope 2C4, and/or (ii) an antibody or immunoconjugate that binds to epitope 4D5.
 51. The method of claim 47, wherein the additional therapeutic agent is selected from trastuzumab, trastuzumab-MCC-DM1 (T-DM1), and pertuzumab.
 52. The method of claim 47, wherein the additional therapeutic agents are (1) trastuzumab or T-DM1, and (2) pertuzumab.
 53. The method of claim 47, wherein the HER2-positive cancer is breast cancer or gastric cancer.
 54. The method of claim 53, wherein the HER2-positive breast cancer is metastatic breast cancer.
 55. The method of claim 53, wherein the HER2-positive breast cancer is early-stage breast cancer.
 56. The method of claim 42, wherein the HER2-positive cancer is recurrent cancer.
 57. The method of claim 56, wherein the recurrent cancer is locally recurrent cancer.
 58. The method of claim 42, wherein the HER2-positive cancer is advanced cancer.
 59. The method of claim 42, wherein the HER2-positive cancer is non-resectable.
 60. A method of treating an individual having a HER2-positive cancer, comprising: a) subjecting the individual to neoadjuvant treatment with the immunoconjugate claim 1, b) removing the cancer by definitive surgery, and c) subjecting the individual to adjuvant treatment with the immunoconjugate of claim
 1. 61. The method of claim 60, wherein the HER2-positive cancer is breast cancer or gastric cancer.
 62. The method of claim 61, wherein the HER2-positive cancer is breast cancer.
 63. A method of inhibiting proliferation of a HER2-positive cell, the method comprising exposing the cell to the immunoconjugate of claim 1 under conditions permissive for binding of the immunoconjugate to HER2 on the surface of the cell, thereby inhibiting proliferation of the cell.
 64. The method of claim 63, wherein the cell is a breast cancer cell or a gastric cancer cell. 